Compare whey protein isolate on the protein per serving, the lactose and sugar on the label, and the cost per 25g of protein. Isolate is whey filtered further than standard concentrate, so it carries more protein per gram and usually costs more, and we show you how to check whether that difference is worth it for you.
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What is whey protein isolate?
Whey protein isolate is whey that has been filtered until at least 89.5% of the dry powder is protein. That is the threshold the American Dairy Products Institute uses: below 89.5% protein it is a concentrate, and at or above it, an isolate.
The extra filtering removes more of the lactose (a milk sugar) and fat, which is why isolate costs more to make and usually more to buy.
What's the difference between whey isolate and whey protein?
Whey isolate is one type of whey protein. "Whey protein" on a tub can mean concentrate, isolate or a mix of the two, so the ingredients list tells you which you're buying. Here is how the two raw ingredients compare under the ADPI specification:
| Per 100g of raw ingredient | Whey concentrate (WPC 80) | Whey isolate (WPI 90) |
|---|---|---|
| Protein (dry basis) | At least 79.5g | At least 89.5g |
| Lactose | No more than 13g | No more than 4g |
| Fat | No more than 2g | No more than 1.5g |
The quick links above take you to concentrate and all whey protein if you want to compare the two directly.
Why does a 90% isolate show less protein on the label?
Because the 90% describes the raw ingredient measured dry, while the nutrition label describes the finished, flavoured powder as sold. ADPI notes that protein content is reported on a dry basis, and flavourings, sweeteners and thickeners take up part of every scoop.
The ingredients list is in descending order of weight, so whey protein isolate should come first. If whey concentrate also appears, the product is really a blend. "We think customers should compare the actual amount of active ingredients they're getting, rather than just the format or marketing," says Andy Arshad, who runs SupplementHQ.
Is whey isolate lactose free?
Not necessarily. Isolate is lower in lactose than concentrate, with an ADPI maximum of 4g per 100g against 13g for WPC 80, but it is only lactose free if the label says so. The NHS describes lactose intolerance as getting symptoms, such as tummy pain, after eating food containing lactose.
A milk allergy is a different thing. Isolate is still a milk protein, and milk is one of the 14 allergens that must be emphasised on the ingredients list, so isolate is not suitable if you have to avoid milk. Look at vegan protein instead.
Is whey isolate worth the extra cost?
Sometimes, and the gap is often smaller than the shelf price suggests. Isolate usually packs more protein into each scoop, so the cost per 25g of protein can sit closer to concentrate than the tub price implies.
How to compare value (example figures, not real products): Concentrate A costs £30 for 1kg, with 24g of protein per 30g scoop: 33 servings, 800g of protein, about 94p per 25g. Isolate B costs £36 for 1kg, with 27g of protein per 30g scoop: 33 servings, 900g of protein, £1.00 per 25g. Isolate B costs 20% more per tub but only about 7% more per 25g of protein.
"Sometimes the premium is justified by formulation, testing or ingredient quality, but sometimes customers are paying mainly for branding," says Andy.
What is hydrolysed whey isolate?
Hydrolysed whey has been partly broken down into smaller protein fragments during manufacturing. Several products in this collection are hydrolysed, and the label will say "hydrolysed" or "hydrolysate".
The evidence for paying extra for it is limited. A 2009 study in young men found higher muscle protein synthesis with whey hydrolysate than with casein at rest, and than with both soy and casein after exercise, but it compared protein types rather than hydrolysed and standard whey. "Where evidence is limited or inconclusive, we should say so openly," says Andy.
Does whey isolate have less sugar and fat?
As a raw ingredient, yes: the specification allows less lactose and fat in isolate than in concentrate. The finished product depends on what is added for flavour, so compare the per-100g figures on the nutrition panel rather than assuming. A "low sugars" claim means no more than 5g of sugars per 100g for a powder.
People searching for isolate on a diet often browse diet and lean protein as well. We don't claim any protein powder causes weight loss.
Which is the best whey protein isolate?
The best isolate for you has the protein per serving you want, a label that clearly shows isolate as the main ingredient, and a sensible cost per 25g of protein. Our guide to reading a supplement label shows what to check, and you can compare isolates against every other type in all protein powder.
We sell the products on this page. That's our commercial interest, and it's why we show the evidence alongside them. This page is general information for adults, not personalised medical advice. Food supplements should not replace a varied, balanced diet.
Written by Andy Arshad, SupplementHQ. Last reviewed 11 October 2026.