# Best Costco Protein Powder > The best Costco protein powder ranked by cost per 25 g of protein, from Kirkland Signature Whey to Ascent and Orgain, plus what Costco actually stocks. - **URL**: https://www.best-proteinpowder.com/best-costco-protein-powder/ - **Updated**: 2026-11-02 - **Author**: [Best Protein Powder Editorial Team](https://www.best-proteinpowder.com/authors/editorial-team/) - **Publisher**: [Best Protein Powder](https://www.best-proteinpowder.com/) --- Seven powders Costco actually stocks, ranked by what matters most in a warehouse club: how much protein you get for your money, then testing and formula. **How we rank:** We judge every powder on the label, not the marketing: protein per scoop, cost per 25 g of protein, the full ingredient list and third-party testing. No paid placements, and commission never sets a ranking. [Read our methodology](https://www.best-proteinpowder.com/how-we-test/) The best Costco protein powder for most people is Kirkland Signature Whey: about 25 g of protein per scoop and the lowest cost per gram of any whey in the warehouse at typical member prices. Optimum Nutrition Gold Standard costs barely more and adds a known manufacturer and a testing claim, and Ascent is the pick if you need a strict sport certification. Costco's range is small and varies by warehouse, so we also explain what it tends to carry and how to compare tubs yourself. ## Our Top Picks | Award | Product | Why | | --- | --- | --- | | Best Value at Costco | [Kirkland Signature Whey Protein Powder (Creamy Chocolate)](https://www.best-proteinpowder.com/best-costco-protein-powder/#kirkland-signature-whey-protein) | The default Costco buy if you tolerate dairy, do not need a sport certification and just want cheap, decent whey. | | Best Name-Brand Value | [Optimum Nutrition Gold Standard 100% Whey](https://www.best-proteinpowder.com/best-costco-protein-powder/#optimum-nutrition-gold-standard-100-whey) | Barely more per gram than Kirkland, with a testing claim and a known manufacturer. The safest everyday Costco pick. | | Best Certified Pick | [Ascent Whey Protein](https://www.best-proteinpowder.com/best-costco-protein-powder/#ascent-whey-protein) | The Costco whey to buy if you compete in a tested sport or simply want the strongest certification for modest extra cost. | | Best Grass-Fed | [Levels Grass Fed Whey Protein](https://www.best-proteinpowder.com/best-costco-protein-powder/#levels-grass-fed-whey-protein-5lb) | A good grass-fed option when your warehouse has it; not worth driving across town for. | | Best Isolate | [Dymatize ISO100 Hydrolyzed Whey Isolate](https://www.best-proteinpowder.com/best-costco-protein-powder/#dymatize-iso100-hydrolyzed) | Pay the step up if regular whey upsets your stomach; otherwise the blends ahead of it are better value. | | Leanest Option | [Isopure Zero Carb Protein Powder](https://www.best-proteinpowder.com/best-costco-protein-powder/#isopure-zero-carb) | The Costco pick for strict low-carb or tight calorie budgets, not for pure value. | | Best Plant-Based | [Orgain Organic Protein Plant-Based Powder](https://www.best-proteinpowder.com/best-costco-protein-powder/#orgain-organic-protein-plant-based) | The only realistic plant option at most warehouses. Buy it for taste and dairy-free convenience, not protein value. | ## 1. Costco Protein Powders Compared at a Glance Here is the short version before the detail. The table lists the seven powders we ranked, with the label figures that matter and a price tier based on cost per 25 g of protein at typical Costco member prices when we checked. Budget means roughly the cheapest third of the market, mid means middle of the road, and premium means you are paying for something other than raw protein value. Exact prices move week to week at Costco, and they differ between the warehouse and Costco.com, so we use tiers rather than dollar figures that would be out of date by the time you read this. | Product | Protein / scoop | Calories | Sugar | Price tier | Certification | | --- | --- | --- | --- | --- | --- | | Kirkland Signature Whey | About 25 g | About 130 | About 1 g | Budget | None confirmed | | Optimum Nutrition Gold Standard | About 24 g | About 120-130 | About 1-2 g | Budget | Informed Choice (by flavor) | | Ascent Whey Protein | 25 g | About 120 | About 1 g or less | Budget to mid | Informed Sport | | Levels Grass Fed Whey | 24 g | About 130 | No added sugar | Mid | None found | | Dymatize ISO100 | About 25 g | About 110-120 | About 1 g | Mid | Informed Choice | | Isopure Zero Carb | About 25 g | About 100-110 | 0 g | Mid to premium | None confirmed | | Orgain Organic Plant-Based | About 21 g | About 150 | Under 1 g | Mid (per 25 g) | USDA Organic only | All nutrition figures come from the brands' labels at the time of writing and vary by flavor. Two things stand out. First, the three cheapest options per gram are all whey blends, which is why Kirkland, Gold Standard and Ascent sit at the top. Second, the gap between the cheapest and the most expensive Costco whey is much smaller than the gap you would see on a supermarket shelf, because Costco only sells large sizes and negotiates hard on all of them. Even the premium end of this list is usually cheaper per gram than the same brand in a small tub at a grocery store. If you only read one line: buy Kirkland Signature Whey for the lowest cost, Optimum Nutrition Gold Standard if you want a known manufacturer and a testing claim for almost the same money, and Ascent if a strict banned-substance certification matters to you. Everything else on the list solves a narrower problem, such as lactose, carbohydrate or dairy avoidance. ## 2. How We Ranked Costco Protein Powder This is a label-and-price analysis, not a taste test. We did not buy and drink every tub. We built the list from products Costco has stocked in US warehouses or on Costco.com, checked each brand's current nutrition label and certification claims, and ranked them on protein per dollar first, then on testing and formula. Where we mention taste or mixing, we are reporting what buyers commonly say, not our own impressions. Our full approach is set out on our [how we test](https://www.best-proteinpowder.com/how-we-test/) page. Protein per dollar means cost per 25 g of actual protein, not cost per tub or cost per scoop. Scoops differ in size and protein content, so a cheaper-looking tub can be the worse deal. The calculation is simple: multiply servings per container by grams of protein per serving to get total protein, divide the price by that total, and multiply by 25. That is the number that lets you compare a 5.4 lb bag of 25 g scoops with a 2.74 lb tub of 21 g servings on equal terms. We rounded the results into budget, mid and premium tiers because Costco prices shift with instant savings, member coupons and online-only deals. After cost, we looked at third-party certification. NSF Certified for Sport and Informed Sport test for banned substances and are the standards that matter to drug-tested athletes. Informed Choice is a related program from the same organisation as Informed Sport, with lower sampling frequency. A powder without a certification is not automatically unsafe, but a certification is independent evidence that what is on the label is what is in the tub, and that is worth something when the manufacturer is not named. ## 3. The Best Protein Powders at Costco, Ranked Ranked by cost per 25 g of protein at typical Costco member prices when we checked, then by certification and formula. Nutrition figures are from each brand's label at the time of writing and vary by flavor. Costco inventory varies by warehouse and region, and some items are sold only on Costco.com, so not every pick will be on your local shelf. ### 1. Kirkland Signature Whey Protein Powder (Creamy Chocolate) **Award:** Best Value at Costco | **Type:** Whey isolate and concentrate blend - **Protein / serving:** About 25 g (label) - **Calories:** About 130 - **Third-party tested:** No sport certification confirmed - **Best for:** Lowest cost per gram Costco's own whey arrived in 2024 as a 5.4 lb bag of roughly 70 servings, and on protein per dollar it is the cheapest whey in the warehouse at typical member prices. Per the label at the time of writing, a scoop gives about 25 g of protein, roughly 130 calories, about 4 g of carbohydrate and 1 g of sugar, from a blend led by whey protein isolate with whey concentrate. Chocolate was the launch flavor; check your warehouse for others. **Bottom line:** The default Costco buy if you tolerate dairy, do not need a sport certification and just want cheap, decent whey. **Pros:** - Budget-tier cost per 25 g of protein, the lowest of any whey at Costco at typical prices - About 25 g of protein per scoop with about 1 g of sugar, per the label - Roughly 70 servings per bag, so one purchase lasts most people two months or more **Cons:** - Costco does not name the contract manufacturer on the bag - No NSF Certified for Sport or Informed Sport listing we could confirm - One or two flavors only, so a bag you dislike is a lot of powder to finish [Check price on Amazon](https://www.amazon.com/s?k=Kirkland%20Signature%20Whey%20Protein%20Powder%20(Creamy%20Chocolate)&tag=sktiger-20) ### 2. Optimum Nutrition Gold Standard 100% Whey **Award:** Best Name-Brand Value | **Type:** Whey blend (isolate listed first) - **Protein / serving:** About 24 g (label, varies by flavor) - **Calories:** About 120-130 - **Third-party tested:** Informed Choice (confirm flavor) - **Best for:** Everyday whey on a budget Gold Standard is the name-brand whey Costco carries most consistently, usually in a tub of around 5 lb or more and a narrow choice of flavors. Per the label at the time of writing, a scoop gives about 24 g of protein for roughly 120 to 130 calories, with whey isolate listed as the first ingredient. Optimum Nutrition promotes Informed Choice on many flavors, so it is the cheapest Costco whey with a credible testing claim attached. **Bottom line:** Barely more per gram than Kirkland, with a testing claim and a known manufacturer. The safest everyday Costco pick. **Pros:** - Budget-tier cost per 25 g in the big Costco tub at typical member prices - Informed Choice promoted on many flavors (confirm your flavor in the database) - Long track record and widely reported to mix easily with a spoon **Cons:** - Costco usually stocks only two or so of the brand's many flavors - Contains whey concentrate, so a little more lactose than a pure isolate - Most flavors use sucralose [Check price on Amazon](https://www.amazon.com/dp/B000GISTZ4?tag=sktiger-20&linkCode=ll1) ### 3. Ascent Whey Protein **Award:** Best Certified Pick | **Type:** Native whey isolate blend - **Protein / serving:** 25 g (label) - **Calories:** About 120 - **Third-party tested:** Informed Sport - **Best for:** Tested athletes, clean label Ascent rolled its Vanilla Bean whey into Costco warehouses nationwide in mid-2025, with chocolate moving to Costco.com, per the brand's announcement. Per the label at the time of writing, a scoop gives 25 g of protein and about 120 calories from native whey isolate, whey isolate and some concentrate, sweetened with stevia. It is Informed Sport certified, which makes it the strongest testing credential among the Costco wheys. **Bottom line:** The Costco whey to buy if you compete in a tested sport or simply want the strongest certification for modest extra cost. **Pros:** - Informed Sport certified, the strictest testing badge among Costco wheys - 25 g of protein for about 120 calories, per the label - Stevia-sweetened with no artificial flavors, per the brand **Cons:** - Costs a little more per 25 g than Kirkland or Gold Standard at typical prices - In-warehouse flavor is usually limited to one; the other flavor is online only - Contains soy lecithin and some whey concentrate [Check price on Amazon](https://www.amazon.com/dp/B01N9V32X2?tag=sktiger-20&linkCode=ll1) ### 4. Levels Grass Fed Whey Protein **Award:** Best Grass-Fed | **Type:** Grass-fed whey concentrate - **Protein / serving:** 24 g (label) - **Calories:** About 130 - **Third-party tested:** No certification found - **Best for:** Grass-fed, no sucralose Levels has appeared at Costco in large bags, though stock is less consistent than Kirkland or Gold Standard. Per the label at the time of writing, a scoop gives 24 g of protein and 5.4 g of BCAAs with no added sugar, from grass-fed, hormone-free whey concentrate. Flavors are sweetened with monk fruit rather than sucralose, and buyers rate the taste highly. It suits shoppers who specifically want grass-fed dairy at a warehouse-club price. **Bottom line:** A good grass-fed option when your warehouse has it; not worth driving across town for. **Pros:** - Grass-fed whey with no added sugar, per the label - Monk fruit sweetening, no artificial sweeteners in the flavored versions - Large bag brings the cost per 25 g down to the mid tier **Cons:** - No third-party certification we could find - Concentrate, so more lactose than an isolate - Not stocked in every warehouse, and stock comes and goes [Check price on Amazon](https://www.amazon.com/dp/B072M8GTXW?tag=sktiger-20&linkCode=ll1) ### 5. Dymatize ISO100 Hydrolyzed Whey Isolate **Award:** Best Isolate | **Type:** Hydrolyzed whey protein isolate - **Protein / serving:** About 25 g (label) - **Calories:** About 110-120 - **Third-party tested:** Informed Choice (brand) - **Best for:** Lactose-sensitive, cutting ISO100 has been sold through Costco.com in large bags, often in a single licensed flavor such as Fruity Pebbles, and occasionally in warehouses. Per the label at the time of writing, a scoop gives about 25 g of protein for 110 to 120 calories with around 1 g of sugar and very little lactose. It carries the Informed Choice logo and is the pick for lactose-sensitive shoppers who still want a Costco price. **Bottom line:** Pay the step up if regular whey upsets your stomach; otherwise the blends ahead of it are better value. **Pros:** - Isolate with very little lactose or fat, per the label - Informed Choice logo on the packaging (confirm your flavor) - Mixes thin and clean, per buyer feedback **Cons:** - Mid-tier cost per 25 g, noticeably more than Kirkland - Costco often carries only one flavor, and sometimes only online - Thinner shake than a blend, which some buyers dislike [Check price on Amazon](https://www.amazon.com/dp/B099J2SWXV?tag=sktiger-20&linkCode=ll1) ### 6. Isopure Zero Carb Protein Powder **Award:** Leanest Option | **Type:** Whey protein isolate - **Protein / serving:** About 25 g (label) - **Calories:** About 100-110 - **Third-party tested:** No sport certification confirmed - **Best for:** Keto, cutting Isopure turns up at Costco in large tubs with a limited flavor choice. Per the label at the time of writing, a scoop gives about 25 g of whey isolate protein for roughly 100 to 110 calories with essentially no carbohydrate or sugar, which makes it the leanest powder you are likely to find in the warehouse. It is also the most expensive per serving of the Costco wheys at typical prices. **Bottom line:** The Costco pick for strict low-carb or tight calorie budgets, not for pure value. **Pros:** - About 25 g of protein for roughly 100 calories, the best protein density here - Essentially zero carbohydrate and sugar, per the label - Isolate base suits most lactose-sensitive stomachs **Cons:** - Mid-to-premium cost per 25 g, the highest of the Costco wheys - Sucralose and an added vitamin blend in flavored versions - No NSF or Informed Sport listing we could confirm [Check price on Amazon](https://www.amazon.com/dp/B000E95HP0?tag=sktiger-20&linkCode=ll1) ### 7. Orgain Organic Protein Plant-Based Powder **Award:** Best Plant-Based | **Type:** Organic pea, brown rice and chia blend - **Protein / serving:** About 21 g (label) - **Calories:** About 150 - **Third-party tested:** USDA Organic; no sport certification - **Best for:** Dairy-free shoppers Orgain is the plant powder Costco has stocked longest, usually in a 2.74 lb tub. Per the label at the time of writing, a two-scoop, 46 g serving gives about 21 g of protein and roughly 150 calories with under 1 g of sugar, sweetened with erythritol and stevia. It is USDA Organic and dairy-free and widely described as easy to drink, but it is the weakest protein deal on this list once you adjust for the smaller dose. **Bottom line:** The only realistic plant option at most warehouses. Buy it for taste and dairy-free convenience, not protein value. **Pros:** - Dairy-free and USDA Organic - Widely reported as one of the easier plant shakes to drink - The most consistently stocked plant protein at Costco **Cons:** - Only about 21 g of protein per two-scoop serving, so the real cost per 25 g is higher than it looks - Erythritol can upset some stomachs - Consumer Reports placed it in its occasional-use group for lead [Check price on Amazon](https://www.amazon.com/dp/B00J074W7Q?tag=sktiger-20&linkCode=ll1) ## 4. What Protein Powder Does Costco Sell? Costco's protein powder range is small compared with a supplement store or Amazon, and that is by design. A typical warehouse carries somewhere between three and six powders at a time, each in one or two flavors and always in large sizes. The core is usually Kirkland Signature Whey and Optimum Nutrition Gold Standard, with a plant option from Orgain and a rotating name-brand whey such as Ascent, Levels, Isopure or Dymatize. Costco.com carries a wider selection than any single warehouse, including some flavors and brands that never reach the shelf. Inventory genuinely varies by warehouse and by region, and it changes through the year. A product can be a nationwide item one season and a regional test the next. Ascent's 2025 move is a good example: per the brand, its vanilla whey went into warehouses nationwide and replaced the chocolate in stores, while chocolate stayed available online. Ka'Chava, SEEQ and other newer brands have appeared at selected Costco locations too. So treat any Costco protein powder list, including this one, as a guide to what Costco tends to carry rather than a promise of what is on your local pallet this week. ### Costco.com versus the warehouse Online and in-store prices are often different. Costco.com prices usually include shipping, so they tend to run a few dollars higher than the same item on the warehouse floor, although online-only deals sometimes reverse that. Some items are sold online only, some only in warehouses, and some in both with different flavors. If cost per gram is your deciding factor, check the warehouse price on the app before ordering online, and watch the monthly member savings book, which features protein powder regularly. ## 5. Is Kirkland Protein Powder Any Good? For most people, yes. On the label, Kirkland Signature Whey is a perfectly normal whey blend: about 25 g of protein, roughly 130 calories and about 1 g of sugar per scoop, from a mix of whey protein isolate and concentrate. That is within a few grams and a few calories of Optimum Nutrition Gold Standard, which has been the reference whey for decades. The main reason to buy it is simple: it is usually the cheapest per gram of protein of any whey Costco sells. The honest caveats are about transparency rather than quality. Costco does not name the company that makes Kirkland whey, and we could not find an NSF Certified for Sport or Informed Sport listing for it. House brands rarely carry sport certifications, so this is not unusual, but it means you are relying on Costco's own quality control rather than an independent tester. For a recreational lifter or someone adding protein to breakfast, that is a reasonable trade for the savings. For a drug-tested athlete, it is not. The other limitation is choice. Kirkland launched in a single chocolate flavor, and a 5.4 lb bag of around 70 servings is a lot of shakes if you find the flavor too sweet or not sweet enough. Buyer feedback has been broadly positive on taste and mixing, with some people finding it a touch thin in water. Because Costco takes returns, the risk is lower than buying a giant bag elsewhere, but a sensible approach is to mix your first few scoops with milk and adjust from there. If you want to compare Kirkland against the wider market rather than just against Costco's shelf, our [best cheap protein powder](https://www.best-proteinpowder.com/best-cheap-protein-powder/) rankings run the same cost-per-gram maths across budget brands sold online. Kirkland is competitive with the cheapest of those, and it beats most of them once you factor in that you are already paying for the membership. ## 6. The Best Protein Powder at Costco for Protein per Dollar Protein per dollar is where Costco earns its reputation. Because the warehouse only sells big sizes, even mid-priced brands land at a better cost per gram than they would in a 2 lb tub at the supermarket. The ranking within Costco is fairly stable, though: Kirkland first, Gold Standard close behind, Ascent and Levels in the middle, and isolates such as ISO100 and Isopure at the top end. Orgain looks cheap per tub, but its 21 g dose per two scoops pushes its real cost per 25 g up into the mid tier. > **THE RULE** > > **Compare cost per 25 g of protein, not cost per tub.** > > Servings per container times grams of protein per serving gives total protein. Divide the price by that, then multiply by 25. A tub that is cheaper on the shelf can easily be the more expensive protein. Sales shift the order more than anything else. Costco runs instant savings on protein powder several times a year, and a discounted name-brand tub can briefly undercut Kirkland. When Gold Standard or Ascent is on instant savings, it is often the better buy for that month. The member savings book and the Costco app both list current deals, and the deal-tracking communities that follow Costco post them as soon as they appear. For a wider look at where to buy protein cheaply, our guide to [buying protein powder on Amazon](https://www.best-proteinpowder.com/amazon-protein-powder/) covers Subscribe and Save, seller checks and how Amazon prices compare. Costco usually wins on the brands it stocks, and Amazon wins on selection. ## 7. Testing and Certification at Costco Only some of the Costco powders carry independent testing badges, and they are not equivalent. Ascent is Informed Sport certified, which means every batch is tested for banned substances before release. Dymatize ISO100 and Optimum Nutrition Gold Standard carry or promote Informed Choice, a related program from the same organisation with less frequent sampling. Kirkland, Levels and Isopure do not carry a sport certification we could confirm, and Orgain carries USDA Organic, which governs farming practices and says nothing about contaminants. A badge on the tub applies to specific products and sometimes specific flavors, so the only reliable check is the certifier's own database. Search the product name and flavor on the Informed Sport or NSF Certified for Sport sites before you rely on it. This matters most for athletes in tested sports, where a positive test is your responsibility regardless of what the label said, and for anyone buying for a teenager who competes. For everyone else, certification is a useful tiebreaker rather than a requirement. A well-known brand with a documented quality system and a long history is a reasonable choice even without a badge, and our page on [whether protein powder is safe](https://www.best-proteinpowder.com/is-protein-powder-safe/) explains where the real risks lie. Plant proteins, for example, tend to carry more heavy metals than whey on average, which is one reason the Orgain tub ranks last here despite being the only plant option Costco reliably stocks. If certification is your top priority and you do not mind paying more, our main [best whey protein powder](https://www.best-proteinpowder.com/best-whey-protein-powder/) rankings include NSF and Informed Sport options that Costco does not carry, and our [protein powder brands](https://www.best-proteinpowder.com/protein-powder-brands/) guide explains how house brands like Kirkland fit into the market. ## 8. Which Costco Protein Powder Should You Buy? ### If you just want cheap, decent whey Buy Kirkland Signature Whey. It has normal macros for a whey blend, the lowest cost per gram in the building and a return policy behind it. If your warehouse is out of stock, Optimum Nutrition Gold Standard is the near-identical fallback, often only slightly more per gram and sometimes cheaper on sale. ### If you compete in a tested sport Buy Ascent, and confirm the flavor in the Informed Sport database. It is the only Costco whey with an every-batch banned-substance certification, and its cost per gram is still far below most certified powders sold elsewhere. Dymatize ISO100 with Informed Choice is the second choice if you need an isolate. ### If dairy bothers you Try an isolate first: Dymatize ISO100 or Isopure. Isolates carry far less lactose than concentrate blends, and many people who bloat on regular whey are fine with them. Our [whey vs whey isolate](https://www.best-proteinpowder.com/whey-vs-whey-isolate/) guide explains the difference. If you avoid dairy completely, Orgain is the plant option Costco stocks most often, but take a larger serving if you are using it to build muscle. ### If you are cutting or eating low carb Isopure Zero Carb has the best protein per calorie and essentially no carbohydrate, so it is the obvious choice if your warehouse has it. Our full guide to the [best low carb protein powder](https://www.best-proteinpowder.com/best-low-carb-protein-powder/) covers the wider market, including options with no sugar alcohols. Whatever you buy, remember that powder is a convenient way to fill a protein gap, not the foundation of a diet. Most people do well getting the majority of their protein from food and using one shake a day where it helps. Our [how much protein do I need](https://www.best-proteinpowder.com/how-much-protein-do-i-need/) guide walks through daily targets by goal. ## 9. Other Costco Protein Products Worth Knowing Costco sells a lot of protein that is not powder, and some of it competes on cost. Ready-to-drink shakes such as Premier Protein and Fairlife Core Power are sold in large cases. Bought by the case, they can come surprisingly close to powder on cost per gram, and they need no shaker or cleanup. For most people they cost more per gram than a tub of Kirkland whey, but if convenience is the reason you skip your shake, a case of bottles may be the better buy. Our [best protein drink](https://www.best-proteinpowder.com/best-protein-drink/) guide ranks the main options. Collagen peptides, such as Vital Proteins, are also a Costco staple. Collagen is popular in coffee and is easy to mix, but it is an incomplete protein, low in leucine and missing tryptophan, so it is not a substitute for whey or a good plant blend if your goal is muscle. We left it out of the ranking for that reason. If you want collagen for its own sake, our [best collagen protein powder](https://www.best-proteinpowder.com/best-collagen-protein-powder/) guide covers it separately. Meal replacements and blended nutrition shakes, such as Ka'Chava in the warehouses that carry it, are a different product again: more calories, more fiber, added vitamins and much less protein per dollar. They suit people replacing a meal, not people adding protein to their day. ## 10. Common Mistakes to Avoid ### Comparing tub prices instead of protein A 2.74 lb plant tub and a 5.4 lb whey bag are not comparable on sticker price. Work out cost per 25 g of protein, using servings per container and grams per serving from the label, and the rankings often flip. Smaller doses per scoop quietly push up the real price. ### Assuming your warehouse has what the website shows Costco.com and individual warehouses carry different products, flavors and prices. A product listed online may never reach your local shelf, and an in-store deal may not appear online. Check the app's warehouse inventory before you make a special trip for a specific tub. ### Buying a giant bag of an untried flavor Costco only sells big sizes, so a flavor you dislike becomes months of grim shakes. If you have never tried a brand, read recent buyer feedback on that flavor, mix your first scoops with milk, and remember the return policy if it is genuinely undrinkable. ### Treating a house brand as certified Kirkland whey has reasonable macros and a low price, but we could not find a sport certification for it. If you are drug tested, buy a product that appears in the Informed Sport or NSF Certified for Sport database, and check the exact flavor. ### Counting collagen as your protein shake Collagen peptides are cheap and easy to mix, but collagen is an incomplete protein with little leucine. It does not stimulate muscle building the way whey or a good plant blend does, so it should not replace your main protein powder. ## 11. Frequently Asked Questions ### What is the best protein powder at Costco? For most people, Kirkland Signature Whey offers the lowest cost per gram of protein, with about 25 g of protein and 1 g of sugar per scoop per the label. Optimum Nutrition Gold Standard costs about the same and promotes Informed Choice testing, and Ascent is the best certified pick with Informed Sport status. ### Does Costco have its own protein powder? Yes. Kirkland Signature Whey Protein launched in 2024 in a 5.4 lb bag of roughly 70 servings, initially in creamy chocolate. Per the label it provides about 25 g of protein from a whey isolate and concentrate blend. Costco does not name the manufacturer, and we could not confirm a sport certification. ### Is Costco protein powder cheaper than Amazon? Often, for the brands Costco stocks. Warehouse prices on large tubs of Gold Standard, Ascent or Kirkland are usually competitive with or below Amazon's, especially during instant savings. Amazon has far more choice, and Subscribe and Save narrows the gap, so compare cost per 25 g of protein on the day you buy. ### Is Kirkland protein powder third-party tested? We could not find Kirkland Signature Whey in the NSF Certified for Sport or Informed Sport databases at the time of writing. Costco runs its own quality control on Kirkland products, but if you are a drug-tested athlete, choose a certified powder such as Ascent and confirm the exact flavor in the certifier's database. ### Does Costco sell plant-based protein powder? Usually one or two options. Orgain Organic Plant-Based Protein is the most consistently stocked, giving about 21 g of protein per two-scoop serving per the label. Other plant brands appear occasionally, especially on Costco.com. If you need more protein per serving, you may have to look outside Costco for a dense pea isolate. ### Why can I not find a protein powder at my Costco? Costco inventory varies by warehouse and region and changes during the year. Some products are online only, some are seasonal, and some are regional tests. Check the Costco app for warehouse stock, ask a member services employee, or order from Costco.com, which carries a wider range than any single warehouse. ### Is Costco protein powder good for weight loss? Any of the Costco wheys can help by making a high-protein, calorie-controlled diet easier to stick to. Isopure Zero Carb has the most protein per calorie, followed by Dymatize ISO100. Protein powder does not burn fat by itself, and our weight loss protein guide explains how to use shakes in a calorie deficit. ## Related Protein Powder Guides - [Best Cheap Protein Powder](https://www.best-proteinpowder.com/best-cheap-protein-powder/): Budget powders ranked on cost per 25 g of protein, with the maths shown. - [Best Protein Powder on Amazon](https://www.best-proteinpowder.com/amazon-protein-powder/): The best sellers worth buying on Amazon, and how to avoid fakes and stale stock. - [Best Whey Protein Powder](https://www.best-proteinpowder.com/best-whey-protein-powder/): The wider whey market ranked on dose, testing and value. ## The Bottom Line Costco is one of the cheapest places to buy protein powder in the US, but only for the handful of products it stocks. Kirkland Signature Whey is the value pick, Optimum Nutrition Gold Standard is the low-risk name brand, and Ascent is the certified choice. Isolates and Orgain solve specific problems at a higher cost per gram. Check your warehouse's stock in the app, compare cost per 25 g of protein rather than price per tub, and buy the powder you will actually finish. If someone in your household has kidney disease, is pregnant or takes medication that affects appetite or digestion, talk to a doctor or registered dietitian about protein targets first. ## More in Protein Powder Guides in this category that pair with what you just read. - [Best Cheap Protein Powder](https://www.best-proteinpowder.com/best-cheap-protein-powder/) - [Best Protein Powder on Amazon](https://www.best-proteinpowder.com/amazon-protein-powder/) - [Protein Powder Brands](https://www.best-proteinpowder.com/protein-powder-brands/) - [Best Protein Powder](https://www.best-proteinpowder.com/best-protein-powder/) About the Author [Best Protein Powder Editorial Team](https://www.best-proteinpowder.com/authors/editorial-team/), Supplements Desk The editorial team reads the label, the certificate and the price per gram of protein before a powder gets near a ranking -- and says plainly when a cheaper tub does the same job. [Full profile](https://www.best-proteinpowder.com/authors/editorial-team/) | [How we test](https://www.best-proteinpowder.com/how-we-test/)