Best Whey Isolate Protein Powder (2026): BulkSupplements
Buy BulkSupplements Whey Protein Isolate. It is unflavored, has nothing added, and is on NSF Certified for Sport, for $1.73 per 25 g of protein. That is the lowest price of the isolates on a testing list. Want it flavored? ON Gold Standard 100% Isolate is $2.05.
By Erin Rose Updated October 18, 2026 How we score
Our pick for: Most people
- Protein
- 25 g a scoopIn a 30 g scoop (4 tbsp)
- Per 25 g of protein
- $1.73Lowest of the isolates on a testing list
- A tub
- $56.97Unflavored, 1 kg, 33 servings, on Amazon
- Testing list
- NSF Certified for SportLists the 1 kg size
- Calories
- 110 a scoop0 g of carbs, 0 g of sugar
- Sweetened with
- NothingUnflavored, so you add your own flavor
Why we pick it It costs the least of the isolates on a testing list, $1.73 per 25 g. NSF Certified for Sport lists the 1 kg size, which is the tub Amazon sells (listing 1797161); it tests each listed lot for drugs banned in sport and checks the label. The label is short: 25 g of protein, 0 g of carbs, 0 g of sugar and 0 g of fat for 110 calories. Nothing is added, so there is no sweetener to read.
What you give up It has no flavor, so you add your own. It is not sold as grass-fed. Want it flavored? ON Gold Standard 100% Isolate costs about 18% more than BulkSupplements per 25 g. See the best whey isolate for your needs below.
The best whey isolate for your needs
BulkSupplements suits most people. If one of these matters more to you, buy the isolate made for it. Each one is on a testing list.
For drug-tested athletes: NOW Sports
Informed Sport tests every batch for drugs banned in sport before it is sold, so any tub you buy is covered. It is sweetened with xylitol and stevia. It costs about 27% more than BulkSupplements per 25 g.
NOW Sports
$2.19 per 25 g · 25 g a scoop · Informed Sport
Low in calories: ON Gold Standard 100% Isolate
It has 100 calories and 1 g of carbs for 25 g of protein, fewer than BulkSupplements or ISO100. It is on Informed Choice and sweetened with sucralose. It costs about 18% more than BulkSupplements per 25 g.
ON Gold Standard 100% Isolate
$2.05 per 25 g · 25 g a scoop · Informed Choice
Which whey isolate is best for weight loss?
None of them burns fat. If you are counting calories, compare calories for the protein you get. ON Gold Standard 100% Isolate, above, has the fewest. ISO100 has 110 calories and 2 g of carbs. BulkSupplements has 110 calories and 0 g of carbs, for 25 g of protein. On Ozempic or another GLP-1 drug, see protein on GLP-1 drugs.
How to choose a whey isolate
Buy one on a testing list for the tub you get
8 of the 10 isolates we checked are on a testing list, and 7 are on one that screens for drugs banned in sport. Informed Sport tests every batch; NSF Certified for Sport tests listed lots; Informed Choice buys tubs from stores. NSF lists each flavor and size on its own, so check that the listing names your tub. Informed Choice and Informed Sport list the product line. See which protein powders are third-party tested.
Compare the cost of 25 g of protein, not the tub
Scoops differ in size and protein, so a cheap tub can cost more per gram. The table below does the math.
Read the sweeteners
Every tub here is vanilla except BulkSupplements. It is unflavored and has nothing added, so there is no sweetener to compare. Of the vanilla isolates on a testing list, Legion Whey+ and BPN use only stevia.
8 whey isolates compared
Cheapest per 25 g of protein first, at Amazon prices checked November 6, 2026. Some prices include an Amazon deal that day, so the order can change. For whey blends and plant powders, see protein powder prices.
| Isolate | Cost per 25 g of protein | Why it is or is not a pick |
|---|---|---|
| BulkSupplements25 g a scoop · 1 kg · NSF Certified for Sport | $1.73 | Our pick: lowest price; unflavored, nothing added |
| ON Gold Standard 100% Isolate25 g a scoop · 44 servings · Informed Choice | $2.05 | 100 calories a scoop, fewer than the other picks |
| Kaged25 g a scoop · 41 servings · Informed Sport | $2.07 | Adds a protease enzyme blend |
| Dymatize ISO10025 g a scoop · 1.3 lb · Informed Choice | $2.12 | Partly hydrolyzed (pre-broken down) whey isolate |
| NOW Sports25 g a scoop · 1.8 lb · Informed Sport | $2.19 | Every batch tested before it is sold |
| Legion Whey+22 g a scoop · 30 servings · NSF/ANSI 173 | $2.25 | Its list checks the label, not banned drugs |
| Thorne21 g a scoop · 30 servings · NSF Certified for Sport, NSF/ANSI 173 | $2.58 | Sweetened with cane sugar |
| BPN25 g a scoop · 25 servings · NSF Certified for Sport | $2.60 | Adds MCT powder |
We also checked 2 isolates that are on no testing list we searched, and left them out.
The proof for our pick
Here is the NSF listing behind the pick, as we saw it.
The NSF listing
Questions people ask
What is the best whey isolate protein powder?
BulkSupplements Whey Protein Isolate. It is on NSF Certified for Sport for the 1 kg size Amazon sells, has 25 g of protein a scoop, has nothing added, and costs $1.73 per 25 g of protein. It is unflavored, so you add your own flavor. The cheapest flavored isolate here on a testing list is ON Gold Standard 100% Isolate, at $2.05 per 25 g.
What is the cheapest third-party tested whey isolate?
BulkSupplements, at $1.73 per 25 g of protein, on NSF Certified for Sport. If you want every batch tested, Kaged is on Informed Sport for $2.07.
Is whey isolate better than regular whey?
It has less lactose and less fat, and it costs more. Whey isolate is typically 0.5 to 1% lactose, against 4 to 8% for whey concentrate (U.S. Dairy Export Council spec sheets). For muscle, the total protein you eat in a day matters more than the type. Our pick for most people is a whey blend: the best protein powder.
Can I take whey isolate if I am lactose intolerant?
Many people can, because isolate has so little lactose. Start with one scoop. If that still bothers you, try a plant powder. Low lactose is not zero, and isolate is still milk protein, so it is not safe with a milk allergy.
Which whey isolates are NSF Certified for Sport?
Of the 10 isolates we checked, BulkSupplements, BPN and Thorne are on NSF Certified for Sport. See every protein powder on a testing list.
Do any whey isolates add amino acids to raise the protein count?
We read the ingredient list of all 10. None lists glycine or taurine, two amino acids sometimes added to pad a protein count. Kaged adds a protease enzyme blend, and BPN adds MCT powder.
How we picked
We read the label and ingredient list of 10 whey isolates sold on Amazon (all vanilla except one unflavored) and searched 5 testing lists for each one. We ranked on three things, in this order: a testing list for the tub you buy, the cost of 25 g of protein, and what else is in the scoop. Not set on isolate? See the best protein powder of any type, the best clear whey, or the protein guide.
Sources
- Amazon listings, Nutrition Facts images and ingredient lists for all 10 isolates, read October 5, 2026.
- NIH Dietary Supplement Label Database: Dymatize ISO100 Gourmet Vanilla, label 302413; ON Gold Standard 100% Isolate Rich Vanilla, label 331939.
- NSF Certified for Sport listing for BulkSupplements, read October 24, 2026: Whey Protein Isolate 1797161.
- NSF Certified for Sport listings, read October 5, 2026: BPN 1778885, Thorne 1513728, Klean 1121764; brand searches for the others.
- Other testing lists, searched October 5, 2026: NSF/ANSI 173; Informed Choice (October 2026); Informed Sport; USP Verified.
- U.S. Dairy Export Council spec sheets: Whey Protein Isolate and Whey Protein Concentrate 80% (typical lactose), read October 5, 2026.