Choose a collagen powder whose dose reaches 15 g — the bottom of the 15 to 30 g range a 2026 tendon review recommends, though a 15-week trial at 15 g found no tendon difference — whose protein was measured on a named lot, that names its animal source and whose certificate says who ran it. Take it with vitamin C, and skip any cosmetic or strength promise: the best evidence on each runs against it.
Collagen is the hardest of the three ingredients in this series to buy well, because the label carries so little of what matters: the useful dose may be larger than the declared serving, and the evidence is narrow. The nine checks below run on the tub and its certificate. The evidence itself, trial by trial, is in the collagen research summary; whether it is worth buying at all, for a man over 45 who lifts, is answered in supplements for men over 45 who lift.
| What to check | What good looks like | The red flag |
|---|---|---|
| Dose | Servings that reach 15 g of collagen in one dose, with the arithmetic shown | A few grams sold on the tendon research |
| Protein figure | Protein per serving measured on a named lot, beside its specification and method | A specification printed as though it were a measurement |
| Source and type | Animal source and collagen type named | “Collagen blend” with neither |
| Hydrolysed or gelatin | Named as what it is | A peptide trademark offered in place of a dose |
| Heavy metals | Lead, arsenic, cadmium and mercury as numbers against a stated limit | “Heavy metals: pass” with no figures |
| The laboratory | Named, with whether it belongs to the maker | A maker’s own figure presented as independent |
| Vitamin C | At least 50 mg alongside the dose, from food or a tablet | Vitamin C sold as the reason to buy the collagen |
| Mixability | Mixing directions that match the powder | A cold-water promise the first glass disproves |
| Promises | Tendon research described with its limits | Any cosmetic or strength promise |
What should you look for in a collagen powder?
On the tub: a dose that reaches 15 g in servings you will actually take, a named animal source and collagen type, whether it is hydrolysed peptides or gelatin, and mixing directions that match the powder. On the certificate: protein measured on a named lot against its specification, the four heavy metals as numbers, and the laboratory named, including whether it belongs to the maker. And no cosmetic or strength promise anywhere on the label.
How much collagen should a serving contain?
Enough to reach 15 g in one dose, the bottom of the 15 to 30 g range a 2026 tendon review recommends, which can mean more than one declared serving. The trial behind that figure gave 15 g of vitamin C-enriched gelatin about an hour before exercise and roughly doubled a blood marker of collagen synthesis, in eight healthy men; a 15-week trial at 15 g a day found no tendon difference at all. Fifteen grams is the studied dose, not a settled one.
Do the division before buying. A 300 g tub at 15 g is 20 doses whatever its servings count says, and a tub that declares a 10 g serving needs one and a half servings for each dose. The 2026 systematic review in the Journal of Functional Morphology and Kinesiology put the higher doses at 15 to 30 g a day, and its lower-dose trials, around 5 g a day, showed no between-group difference in tendon stiffness. The derivation and timing are in how much collagen for tendons, and the serving-against-dose arithmetic in how many doses are in the tub.
What is the best collagen for tendons?
No product has been shown to be best, so the honest answer is a dose rather than a brand: about 15 g of hydrolysed collagen or gelatin with vitamin C, before training that loads the tendon. A 2026 systematic review graded the evidence strong for larger tendon cross-sectional area and stiffness with training, from trials that gave 5 g or 30 g a day, and recommends 15 to 30 g. A trial at 15 g a day in 39 men over 15 weeks, which the review did not include, found no difference from placebo on any tendon measure.
Both findings carry their limits. The review covered eight randomised trials and 257 participants aged 18 to 52, 246 of them men, over three to fifteen weeks, and named small samples and short durations as its own limitations. The null trial, Balshaw and colleagues’ 2023 study in Medicine & Science in Sports & Exercise, imaged the tendon by MRI in recreationally active young men. And the trial behind the 15 g, Shaw and colleagues’ 2017 study in the American Journal of Clinical Nutrition, had eight participants and measured a blood marker, not a tendon. A label claiming more than this claims more than the research found; the whole case is in does collagen actually work.
Is hydrolysed collagen better than gelatin?
Not on any measure the main collagen trials compared. Hydrolysed collagen is gelatin cut into shorter peptides, so it dissolves into a drink instead of setting, and its amino acids are largely the same. The trial behind the 15 g dose used vitamin C-enriched gelatin; the 39-man, 15-week tendon trial used hydrolysed peptides and found no tendon difference. For a buyer the choice is mostly format, and the dose matters more than either.
A peptide trademark or the word bioactive names a manufacturing claim, not a dose, and what it does and does not buy is set out in bioactive collagen peptides vs collagen peptides. The two formats are compared directly in collagen peptides vs gelatin, and the food version of the question in collagen vs bone broth.
Does the type of collagen matter?
Less than the label suggests. A type number names the collagen family in the tissue a powder was made from, so it describes origin rather than effect, and none of the main tendon trials compared one type against another. What a buyer can usefully check is that the label names an animal source and a type at all, and that it does not offer a type number in place of a dose.
The type families are explained in collagen types explained, and the commonest sourcing question in bovine vs marine collagen.
What should a collagen certificate of analysis show?
Protein measured on a named lot against its specification, with the method; lead, arsenic, cadmium and mercury as numbers against a stated limit; a microbiology panel; and the name of the laboratory, including whether it belongs to the company that makes the powder. A maker’s own laboratory can produce real numbers, but it is a weaker check than an outside one, and the document should make clear which it is.
For lead, one comparison a certificate may print is California’s Proposition 65 maximum allowable dose level, 0.5 micrograms a day (OEHHA). Two cautions travel with it. The limit is per day while a certificate reports per serving or per gram, so the two compare only after the figure is run forward to the dose actually taken; and a figure under it means a warning is not required, not that a powder is graded pure. The same discipline applies to protein: a figure printed beside its specification is a measurement only if the document says it was measured. The full method is in what is a certificate of analysis, and every label term in the supplement label glossary.
Should collagen be taken with vitamin C?
Yes, if the aim is the tendon protocol. The NIH Office of Dietary Supplements states that “vitamin C is required for the biosynthesis of collagen,” among other compounds. Beyond that, the trial behind the 15 g dose used vitamin C-enriched gelatin, and the 2026 review’s conclusion pairs 15 to 30 g of collagen with at least 50 mg of vitamin C. A medium orange carries about 70 mg, and the RDA for men is 90 mg a day (ODS).
The vitamin C does not have to be in the tub, and a collagen sold on its added vitamin C is selling the cheapest part of the protocol. The adult upper level is 2,000 mg a day (ODS), far above anything a collagen protocol uses. And the null 15 g trial above is the reason the pairing is a protocol rather than a promise.
What the research does not show
It does not show a strength effect. The 2026 review graded the evidence strong against an effect on muscle strength. The 2024 meta-analysis in Sports Medicine by Bischof and colleagues, 19 studies and 768 participants, found maximal strength SMD 0.19 (p<0.01), on evidence its authors rated low certainty: statistically detectable and trivially small.
It does not show collagen working as protein for muscle. Aussieker and colleagues gave 45 young recreational athletes 30 g of collagen, 30 g of whey or a placebo after resistance exercise; collagen raised neither muscle connective nor myofibrillar protein synthesis above placebo, while whey raised myofibrillar synthesis. Collagen is a different purchase from protein, as collagen vs whey protein sets out.
It does not support a cosmetic promise. Myung and Park’s 2025 meta-analysis of 23 randomised trials and 1,474 participants found a pooled cosmetic effect that disappeared in the trials without pharmaceutical-company funding and in the high-quality trials.
It does not cover the oldest readers. The review’s participants were 18 to 52 and the null trial’s were young men, so men well past 50 sit outside the measured range. And it does not settle a ceiling: the higher doses spanned 15 to 30 g, and no trial here was designed to find where more stops adding anything.
Where Under Load sits against these checks
Under Load is collagen peptides, types I and III, bovine, grass-fed, from Brazil, one ingredient, 350 g. The declared serving is 10 g, two 5 g scoops, 35 servings. Our protocol is a directions statement, never a serving: 15 g, three scoops, 30 to 60 minutes before training, with 50 to 100 mg of vitamin C — 23 whole doses per tub. We use 15 g because it is the bottom of the 15–30 g daily range the 2026 tendon review recommends with training. Its certificate was run by ViaCore, the manufacturer’s own laboratory, on lot 121125450: 9.8 g measured per 10 g serving; 1.5 servings is 14.7 g by arithmetic. That is the weaker kind of check, and the document is on Testing & Certification. The panel also says collagen does not mix well in cold water: warm water first, ice after.
The same checks for the other two ingredients are in how to choose a creatine supplement and how to choose a magnesium supplement; their evidence is in the creatine research summary and the magnesium research summary, and every form side by side on the supplement forms hub.
Sources
- Shaw G, Lee-Barthel A, Ross ML, Wang B, Baar K. Am J Clin Nutr 2017;105(1):136–143. PubMed 27852613
- Buchalski A, Jeanfavre M, Altorelli C, et al. J Funct Morphol Kinesiol 2026;11(1):130. PubMed 41900537
- Balshaw TG, Funnell MP, McDermott EJ, et al. Med Sci Sports Exerc 2023;55(11):2083–2095. PubMed 37436929
- Bischof K, Moitzi AM, Stafilidis S, et al. Sports Med 2024;54(11):2865–2888. PubMed 39060741
- Aussieker T, Hilkens L, Holwerda AM, et al. Med Sci Sports Exerc 2023;55(10):1792–1802. PubMed 37202878
- Myung SK, Park Y. Am J Med 2025;138(9):1264–1277. PubMed 40324552
- NIH Office of Dietary Supplements. Vitamin C: Fact Sheet for Health Professionals (updated 31 July 2025). NIH Office of Dietary Supplements
- California Office of Environmental Health Hazard Assessment. Lead: Proposition 65 listing and safe harbor levels. oehha.ca.gov