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Cheapest overallPeak Supps
Soy Protein Isolate 90%86 bought this week
86bought this week91% protein · 27.3g / 25g serving
Bag · 5kg
£44.99
£0.25 / 25g protein
Whey Isolate
Cheapest Whey Isolate UK
Compare protein prices from MyProtein, Bulk, Optimum Nutrition and 85+ other UK retailers. Every product ranked by cost per 25g of protein. Free, updated weekly. Whether you are buying whey concentrate, whey isolate, vegan protein, casein, or a mass gainer, every bag is normalised to the same metric so you can compare across brands, sizes, and protein percentages without doing the maths yourself. No sponsored rows, no affiliate-biased rankings. The cheapest option sits at the top because it is the cheapest, not because a brand paid for placement.
82products tracked
98+retailers
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This week · editorial podium
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Hand-picked by our nutrition team every Monday, 07:00. Scored on £/25g protein, clean-label, and weekly velocity.
Showing 82 whey isolate products
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About Whey Isolate Protein
Whey isolate goes through additional filtering to remove most of the fat and lactose, resulting in a high quality protein source that is typically 90% or more protein by weight. It delivers a complete amino acids profile — including all essential amino acids needed for muscle repair and recovery — making it the go-to choice for people on a strict calorie budget, those with mild lactose sensitivity, or anyone who wants maximum protein per scoop.
We track whey isolate products across UK retailers, all normalised to price per 100g so you can compare fairly regardless of bag size or serving suggestion. You will typically pay more per 100g than concentrate, but you are getting significantly more high quality protein per gram of powder.
If budget is your main concern and you tolerate lactose well, whey concentrate may be the better value option. For a completely dairy-free alternative, browse our vegan protein comparison.
Methodology
How we rank every bag.
Independent, transparent, and updated weekly. Here's what goes into each score.
01
Cost normalised to £/25g
Every bag divided by its true protein weight, so you see the real cost of a scoop across any size or brand.
02
Protein quality, not just %
Protein %, leucine and digestibility feed the Performance score. A 90% isolate and a 90% vegan blend are not the same.
03
Clean-label audit
Ingredient count, artificial sweeteners, added sugars, third-party certifications. 0 to 100 score.
04
Social and review signals
Weekly purchase volume and weighted review scores surface what people actually re-buy, not just what ranks on search.
Questions, answered.
Whey concentrate contains 70-80% protein with some fat and lactose. Whey isolate is filtered further to 90%+ protein with minimal fat and lactose, making it better for those who are lactose intolerant or want a leaner protein source.