Is Collagen Bad for Your Kidneys or Liver? The Trial Record

No kidney or liver signal has appeared in the collagen trial record: in the trials that ran blood safety tests, up to 12 months at 2 to 5 g a day, kidney and liver markers did not change, and across 35 randomised trials of 3,165 people adverse events were no more frequent than in the control groups.^{1, 2, 3, 4} Two groups ask a GP first: people who form calcium-oxalate kidney stones, and anyone with a protein limit set by a renal team, because collagen is protein and counts towards it. No trial has included anyone with kidney or liver disease. Part of the Wellgard collagen guide; cautions beyond the kidneys and liver are on collagen side effects.

Is collagen bad for your kidneys?

Not in any trial that looked. The longest is the 12-month bone study: 131 postmenopausal women, mean age 64, took 5 g a day or a control; its full paper reports that the blood safety panel, "hemogram, kidney, liver and inflammatory parameters", showed no clinically relevant change, and that women with "renal or liver diseases induced by a high protein load" were excluded, so the result cannot be stretched to kidney disease.¹ The table lists the three trials that describe their kidney or liver tests; none prints a creatinine or eGFR value, so this page cannot either.^{1, 2, 3}

One caution survives that record. Hydroxyproline, collagen's signature amino acid, is partly broken down to glycolate and oxalate. When volunteers on a controlled diet ate 30 g of gelatine rather than whey, urinary glycolate rose 5.3-fold and oxalate 43%, with changes at 5 and 10 g loads and none at 1 and 2 g; in five healthy men taking 30 g of gelatine for three days, glycolate rose but oxalate excretion and calcium-oxalate supersaturation did not change.^{5, 6} Neither study counted stones, and no trial has reported a kidney event on collagen. Someone who has formed a calcium-oxalate stone keeps to a moderate daily serving and asks a GP, as the NHS kidney stones page (reviewed 17 September 2026) says of any dietary change: "do not make changes to your diet without speaking to your doctor". The same page lists "eat a high-protein, low-fibre diet" among the reasons stones return and advises adults to "drink 2.5 to 3 litres of water each day".⁷

Can you take collagen if you have kidney disease?

That is your renal team's question: no collagen trial has recruited anyone with chronic kidney disease, and the 12-month trial excluded it.¹ What is known is simpler: collagen is protein. It lacks tryptophan, and a modelling study found it can make up as much as 36% of a day's protein with amino-acid needs still met.⁸ So if a dietitian or renal team has given you a protein figure, a serving of collagen counts towards it, gram for gram. The NHS chronic kidney disease page (reviewed 22 March 2023; its next review was due in March 2026 and has not yet appeared) says "If you have CKD, you may not need a special diet", that a dietitian advises when potassium and phosphate run high, and, of nutritional supplements, "Check with a doctor or pharmacist" first, because "These can sometimes affect your kidneys".⁹ Collagen as protein has the amino-acid detail.

Does collagen increase creatinine levels?

No trial has shown that it does, and the question is mostly one of measurement. Creatinine is a waste product of muscle metabolism; the NHS explains that the kidney blood test "measures the levels of a waste product called creatinine in your blood" and that an eGFR is calculated from it, where "Healthy kidneys should be able to filter more than 90ml/min" (page reviewed 22 March 2023, review overdue).¹⁰ Collagen is not creatine, the supplement that is turned over into creatinine: creatine vs creatinine explains that marker, and collagen and creatine covers taking both. In the two trials that name creatinine, it stayed "within normal ranges" on 5 g for six months and showed "no clinical changes" on 2 g for 12 weeks, the latter in the full paper.^{2, 3} A creatinine-based estimate, as a 2024 case report on a kidney-transplant recipient who had taken up bone broth puts it, "is well known to be impacted by many different factors", and its authors argue for a second marker, cystatin C, alongside it.¹¹ So tell whoever takes your blood what you take, collagen included.

Is collagen bad for your liver?

No trial reports a liver signal. The trials that measured liver enzymes report ALT and AST "within normal ranges" after six months at 5 g, "no clinical changes in the levels of liver enzyme" (in the full paper) after 12 weeks at 2 g, and liver parameters without clinically relevant change after 12 months at 5 g.^{1, 2, 3} A liver that is not well is a question no trial has asked: the 12-month trial excluded liver disease and no other trial recruited it. The NHS cirrhosis page (reviewed 10 February 2025) says "check with a pharmacist or doctor before taking any medicines, including herbal medicines".¹² With any liver diagnosis the liver team or GP decides; this page does not call collagen safe for it.

Does marine collagen affect the kidneys differently?

No. Fish and bovine collagen are the same type I protein hydrolysed to the same kinds of peptides. Two of the trials in the table are marine, the six-month menopause trial and the 2 g skate-skin trial, and their kidney and liver readings match the 12-month trial's.^{1, 2, 3} Heavy metals are the marine question people usually mean; the law sets the same limits for every collagen sold as food whatever the animal, and what is marine collagen has the contaminant surveys.

How much collagen is too much for your kidneys?

No upper limit for collagen exists in UK law, because it is protein, and the modelling study puts the ceiling at about 36% of a day's protein, far above the 2.5 to 15 g a day the trials used.⁸ The kidney-marker data cover 2 to 5 g a day for up to a year; the oxalate studies used single loads of 5 to 30 g of gelatine, and the only kidney-related change on record at those amounts is that urine chemistry.^{1, 5, 6} Too much collagen has the upper-dose trials in full.

Who should ask a GP before taking collagen?

The two kidney groups first: anyone who has formed a calcium-oxalate kidney stone, and anyone with chronic kidney disease or a protein limit set by a renal team.^{5, 7, 9} Then anyone with a liver diagnosis, who follows the NHS cirrhosis wording and asks a pharmacist or doctor.¹² Collagen side effects adds fish allergy with marine collagen, beef or alpha-gal allergy with bovine, pregnancy and anyone timing levothyroxine, and answers the gout worry (collagen is a purified protein with very little purine, and no trial has reported a change in uric acid on it). Collagen with blood pressure tablets or statins has its own page in this series; lupus, which can affect the kidneys, is on the autoimmune page.

Frequently asked questions

Is hydrolysed collagen safe for kidneys?

Hydrolysed collagen and collagen peptides are the same product, the one every trial in the table used. In healthy adults it has not shown a kidney signal in trials of up to 12 months; "safe" for a particular pair of kidneys is a GP's or renal team's word, and the two cautions stand.^{1, 2, 3}

Can collagen cause kidney stones?

No study has counted stones on collagen. A 30 g gelatine load raised urinary oxalate 43% in one study and left it unchanged in another.^{5, 6} Someone who forms calcium-oxalate stones keeps to a moderate serving, drinks the water the NHS advises, and speaks to a GP before changing their diet.⁷

Is collagen safe to take with liver disease?

Untested: no collagen trial has included anyone with liver disease, so the "within normal ranges" results above belong to healthy livers, and the NHS cirrhosis wording, check with a pharmacist or doctor first, applies.^{1, 2, 3, 12}

Does collagen affect blood tests?

Plain collagen peptides have not changed a laboratory panel in any trial that ran one.^{1, 2, 3} Two notes: a creatinine reading is "impacted by many different factors", so tell the person taking your blood what you take; and some collagen blends add biotin, which can affect thyroid blood tests, as collagen and thyroid medication explains.¹¹

Sources

1. König D, et al. Specific collagen peptides improve bone mineral density and bone markers in postmenopausal women: a randomized controlled study. Nutrients, 2018. PubMed 29337906.
2. Duangjai A, et al. Calcium and vitamin D supplementation with and without collagen on bone density and skin elasticity in menopausal women: a randomized controlled study. Clinics and Practice, 2025. PubMed 41002783.
3. Tak YJ, et al. Effect of oral ingestion of low-molecular collagen peptides derived from skate skin on body fat in overweight adults: a randomized, double-blind, placebo-controlled trial. Marine Drugs, 2019. A manufacturer among the authors. PubMed 30866485.
4. Liang CW, et al. Efficacy and safety of collagen derivatives for osteoarthritis: a trial sequential meta-analysis. Osteoarthritis and Cartilage, 2024. PubMed 38218227.
5. Knight J, et al. Hydroxyproline ingestion and urinary oxalate and glycolate excretion. Kidney International, 2006. PubMed 17021603.
6. Rodgers A, et al. Theoretical and laboratory investigations of the effects of hydroxyproline ingestion on the metabolic and physicochemical risk factors for calcium oxalate kidney stone formation in a small group of healthy subjects. International Urology and Nephrology, 2019. PubMed 31161522.
7. NHS. Kidney stones. Page last reviewed 17 September 2026 (read 12 October 2026). nhs.uk/conditions/kidney-stones.
8. Paul C, Leser S, Oesser S. Significant amounts of functional collagen peptides can be incorporated in the diet while maintaining indispensable amino acid balance. Nutrients, 2019. PubMed 31096622.
9. NHS. Chronic kidney disease: living with. Page last reviewed 22 March 2023 (next review was due 22 March 2026; read 12 October 2026). nhs.uk/conditions/kidney-disease/living-with.
10. NHS. Chronic kidney disease: diagnosis. Page last reviewed 22 March 2023 (next review was due 22 March 2026; read 12 October 2026). nhs.uk/conditions/kidney-disease/diagnosis.
11. Chandler S, et al. Bone broth ingestion and acute kidney injury following kidney transplant: a role for cystatin C. BMJ Case Reports, 2024. PubMed 38388200.
12. NHS. Cirrhosis. Page last reviewed 10 February 2025 (read 12 October 2026). nhs.uk/conditions/cirrhosis.

General information, not medical advice: with kidney disease, a history of kidney stones, a liver condition or any regular medicine, ask your renal or liver team, GP or pharmacist before collagen.