What is the best whey isolate?

An isolate that delivers at least 20 g of complete whey protein per serving, with a good protein percentage and an honest label. At the top of the list are the isolates rated A+: 25 g or more per serving, leucine and the full amino acid profile stated. The order cannot be bought: partner or not changes nothing about the score.

What does the best isolate cost per shake and per month?

Count on one shake of 30 grams a day: that shows what the difference in price per kilo means for your budget.

Which whey isolate has the best value for money?

An isolate rated A with a low price per kilo. The score guarantees the protein quality, the price per kilo makes the difference. The table further down shows the cost per shake and per month; for the lowest price per kilo across every shop, see the cheapest whey isolate.

Whey isolate or concentrate?

Isolate is more filtered: more protein, almost no lactose or fat, but more expensive. For most athletes a good concentrate is enough; see the best whey protein.

Does whey isolate contain lactose?

Hardly any. Many people who are sensitive to lactose tolerate it better than a concentrate; with a strong intolerance check the label or choose a plant-based protein.

Did Dr Diederik Smit test every isolate?

No. He reviewed the medical criteria of the whey scorecard. The editors applied those criteria to the isolates sold in the UK.

What about clear whey?

Clear whey is an isolate that drinks like a squash. It is not in this list; see the cheapest clear whey for the prices.

Best whey isolate UK 2026: SupplementScore comparison

Product	Per shake (30 g)	Per month
Myprotein Impact Whey Isolate Powder £43.50 per kilo	£1.30	£39.15
Optimum Nutrition Gold Standard 100% Isolate Whey Protein £84.44 per kilo	£2.53	£76.00

Whey isolate is the most filtered whey: more protein per 100 g, almost no lactose or fat. A whey concentrate sits around 70 to 75% protein; a good isolate usually contains 80 to 90%. It costs more per kilo, but per gram of protein the gap shrinks. The effect of extra protein is well established: the largest meta-analysis (Morton 2018, source 1 at the bottom) shows that protein supplementation increases muscle mass and strength with resistance training. Below, every rated whey isolate sold in the UK in the order of the SupplementScore, partner or not, with its protein per serving, the reason for the grade and today’s price. Only the price per kilo matters to you? See the cheapest whey isolate.

What do SupplementScore A and A+ mean for an isolate?

The score judges the quality and effectiveness of the protein, not taste or sweetener. Isolate is judged on its own protein-percentage threshold, stricter than the one for concentrate.

Score	What we established	What it gives you
A	At least 20 g of complete whey protein per serving, a good protein percentage for an isolate and an honest label.	An effective isolate. Often also the best buy when the price per kilo is low.
A+	Everything of an A, plus 25 g of protein or more per serving, leucine stated and the full amino acid profile on the label.	Maximum transparency about what you take. Not more effect than a good A.
B	Good protein with a reservation: just under 20 g per serving, or added single amino acids that make the protein figure less telling.	Perfectly usable; look at the serving size.
No score	The product cannot be linked unambiguously to the scorecard (blend, bundle, missing label data).	Better no badge than a rating on the wrong product.

Amino spiking (cheap amino acids counted as protein) caps a product at C; a clearly misleading label gives a D. Read the full method and check the released ratings in the open score feed.

Isolate, concentrate or clear whey: which to choose?

Type	Characteristics	For whom
Whey isolate	More filtered: often 80 to 90% protein, almost no lactose or fat, more expensive per kilo.	If you digest lactose poorly or want as little fat and carbohydrate as possible.
Whey concentrate	Around 70 to 75% protein; the best price per gram of protein.	The best all-round choice for most athletes.
Clear whey (isolate)	The same protein as isolate, but drinks like a squash instead of a milkshake.	If you do not like the thick texture of a shake.

What we reject

These signals on a label make us advise against an isolate:

An "isolate" that is really a blend: If isolate is only one ingredient next to concentrate, the powder is a blend. We then judge it on the concentrate threshold, not as an isolate.
Amino spiking ("glutamine peptide", added glycine or taurine): Cheap amino acids that count towards the protein content on the label. The standard nitrogen test (Kjeldahl) does not see the difference. If it is in the ingredient list, the protein percentage is flattered.
More than 5 g of sugar per serving: Pointless in an isolate: it lowers the protein percentage and only adds calories.
Proprietary blends without doses: If a brand does not dare to say how much of each ingredient there is, you cannot check the quality.

What should you look out for?

Check that isolate is the only protein ingredient: a blend with concentrate is not an isolate. Then look at the protein per serving and the percentage per 100 g, and compare the price per kilo or per gram of protein: a good isolate sometimes beats a cheap concentrate. Looking mainly for the lowest price per kilo? See the cheapest whey isolate.

How this list is put together

The list sorts first by SupplementScore (A+ before A). Within the same score our partners come first, then the other brands, each on user rating; the score itself cannot be bought and the same public rules apply to partners and non-partners. We only link products that we can tie unambiguously to the scorecard; in doubt we show no score. The criteria were medically reviewed by Dr Diederik Smit, endocrinologist; he did not assess each of these British products separately. Prices are measured daily; the scores change only when the label changes.

What proof sits behind each score?

Every product in the list above has a proof passport: protein per serving and type, the reason for the grade, and whether we earn a commission. Partner or not changes nothing about the score.

Medical review: The whey scorecard (v3.2: protein per serving, protein percentage with its own threshold for isolate, leucine, label honesty) was medically reviewed by Dr Diederik Smit, endocrinologist. He did not assess each of these products sold in the UK separately: the editors applied his criteria to the British variants.

Product	Score	Protein and type	Why this score?	Public proof
Myprotein Impact Whey Isolate PowderAccording to the criteria reviewed by Dr Diederik Smit · Partner: we earn a commission if you buy through our link	A+	25 g protein per serving (30 g)	At least 25 g of complete whey protein per serving, a high protein percentage for an isolate, leucine and the full amino acid profile stated.	No public, product-specific proof found. That is not a sign of poor quality; the brand simply does not (yet) stand out with verifiable proof.
Kruidvat Kruidvat 100% Isolate Whey ProteinAccording to the criteria reviewed by Dr Diederik Smit · Not a partner: no commission	A+	26 g protein per serving of 30 g, 2.7 g leucinewhey isolate (98%), 87% protein	At least 25 g of complete whey protein per serving, a high protein percentage for an isolate, leucine and the full amino acid profile stated.	No public, product-specific proof found. That is not a sign of poor quality; the brand simply does not (yet) stand out with verifiable proof.
Optimum Nutrition Gold Standard 100% Isolate Whey ProteinAccording to the criteria reviewed by Dr Diederik Smit · Partner: we earn a commission if you buy through our link	A	25 g protein per servingwhey isolate, 81% protein	At least 20 g of complete whey protein per serving, a good protein percentage for an isolate and an honest label.	No public, product-specific proof found. That is not a sign of poor quality; the brand simply does not (yet) stand out with verifiable proof.
Decathlon Whey-protein Whey IsolateAccording to the criteria reviewed by Dr Diederik Smit · Not a partner: no commission	A	25 g protein per serving of 30 gwhey isolate (96%), 82% protein	At least 20 g of complete whey protein per serving, a good protein percentage for an isolate and an honest label.	No public, product-specific proof found. That is not a sign of poor quality; the brand simply does not (yet) stand out with verifiable proof.

Last tested on 19 October 2026 by the editors; whey scorecard SupplementScore v3.2 applied to the isolates sold in the UK, criteria medically reviewed by Dr Diederik Smit; scientific claims checked against the sources at the bottom

Sources

See the best whey →

What is the best whey isolate in the UK in 2026?

How we rate an isolate

Which whey isolate has the best SupplementScore?

Questions