Marine Collagen Side Effects: What to Know, Who Should Avoid It and Marine vs Bovine

Medically reviewed by Dr. Reina Punj, MBBS, PG Diploma in Endocrinology (University of South Wales), Lead Physician, Excelgenics Clinical Panel.

Marine collagen side effects are uncommon and usually mild: in clinical trials, collagen supplements have generally been well tolerated, and the complaints people mention most are mild stomach upset, bloating or a feeling of fullness. The most important risk is allergy, so people with a fish allergy should avoid marine collagen. This article explains what marine collagen is, the side effects of marine collagen powder and capsules, how marine collagen compares with bovine collagen, and who should be careful.

For how collagen supplements work and what to look for on a label, see our Marine Collagen Supplements Guide.

What is marine collagen?

Collagen is the main structural protein in skin, tendons and bone. Marine collagen comes from fish skin or scales and is mainly type I collagen, the type found most in human skin. In supplements it is usually hydrolysed: broken down into smaller pieces called collagen peptides, which are easier to digest and mix. Marine collagen is sold as powders, tablets and capsules, often combined with hyaluronic acid, vitamin C and antioxidants.

Marine collagen side effects: what the evidence shows

A 2019 systematic review of 11 randomised, placebo-controlled trials (805 participants) of oral collagen for skin and other dermatological uses concluded that collagen supplementation is generally safe, with no adverse events reported in those trials. The Harvard T.H. Chan School of Public Health similarly notes that research has not shown negative side effects in people given collagen supplements, while pointing out that the research is limited and often industry-funded.

"Generally well tolerated" does not mean "no side effects". Trials are short and often small. Effects people may notice include:

• Digestive upset: mild stomach discomfort or bloating.
• A feeling of fullness: collagen is a protein, and larger powder servings can feel filling.
• Taste and smell: some people find unflavoured fish-based powders have a fishy taste or smell; capsules avoid this.

If any of these persist, stop taking it and speak to your doctor or pharmacist.

Marine collagen powder side effects vs capsules

Powders usually deliver several grams of collagen per serving, while capsules deliver less and often add other ingredients. With powders, digestive effects and taste are the more common complaints. With capsules, the main thing to check is the other ingredients, because these, rather than the collagen, are what can interact with medicines (see below).

Fish allergy: the key risk

Collagen itself can be an allergen. Researchers identified fish collagen as a fish allergen in 2001, separate from parvalbumin, the protein that causes most fish allergies. Serious reactions have been reported: in one published case, a 30-year-old woman with eczema (atopic dermatitis) had anaphylaxis after eating a supplement containing hydrolysed fish collagen. Her doctors believe she had become sensitised through a fish-collagen face cream applied to her damaged skin. Interestingly, she reported no reactions to eating fish, which suggests that a reaction to fish collagen is possible even without a typical fish allergy.

Such reactions appear to be rare, but they matter:

• If you have a fish allergy, avoid marine collagen.
• If you have had a reaction to fish gelatin or a collagen skin product, speak to your doctor first.
• Seek urgent medical help for swelling of the lips, face or throat, difficulty breathing, or a widespread rash after taking any supplement.

Heavy metals and contaminants

Because marine collagen comes from fish, people reasonably ask about heavy metals. A 2025 study in Open Medicine tested fish-collagen supplements from brands that named the fish species on the label and found arsenic, lead, cadmium and chromium in fish-derived samples, with mercury in only a few. None exceeded the EU limits the authors used, and estimated daily intakes were below tolerable levels, so the authors judged the products safe at recommended doses. They still described lead levels as a concern, called for more data, and noted that their assessment did not account for people taking several supplements at once.

The practical advice is to choose products from brands that can tell you the fish source and share contaminant test results on request, and to keep to the label dose.

Other ingredients in marine collagen supplements: interactions

Many marine collagen products are blends, and some of the added ingredients have known cautions. Radia Marine Collagen + Hyaluronic Acid is an example. Per 2-capsule daily serving it contains marine collagen peptides (type I & III) 500 mg, low-molecular-weight hyaluronic acid 100 mg, grape seed extract (95% OPC) 100 mg, vitamin C 65 mg, CoQ10 60 mg, lycopene 10 mg, vitamin E 10 mg, zinc 5 mg, black pepper extract 5 mg and astaxanthin 4 mg. The dose is 2 capsules daily after a meal. It is fish-derived, so it is not vegetarian and is not suitable for people with a fish allergy.

• CoQ10: has been reported to reduce the effect of warfarin, and may interact with insulin and other diabetes medicines.
• Black pepper extract (piperine): has been shown to inhibit CYP3A4 and P-glycoprotein, which handle many medicines, so it can change how some drugs are processed.
• Vitamin E: large supplemental doses may increase bleeding risk with blood thinners such as warfarin. The amount needed for a clinically significant effect is unknown but is thought to be well above the 10 mg in a serving of Radia. Still, count it if you take other vitamin E supplements.
• Doubling up: check other products for vitamin C, zinc and CoQ10 so you do not take more than you intend.

If you take any regular medicine, especially a blood thinner or diabetes medicine, speak to your doctor before starting a collagen blend.

Pregnancy and breastfeeding

There is little safety research on collagen supplements in pregnancy or breastfeeding, and many blends contain other ingredients, such as CoQ10 and piperine, that are not recommended without medical advice at these times. Consult your doctor before use.

Marine collagen vs bovine collagen

Is one better? Neither has been clearly shown to be better for skin. Most skin trials used 2.5–10 g of collagen peptides a day, from a range of sources, and a 2025 review in The American Journal of Medicine found that the benefits reported came mainly from industry-funded and lower-quality studies, while higher-quality trials found no significant effect. Choose based on your diet, beliefs, allergies and the format you will actually take.

Is marine collagen vegan?

No. Marine collagen comes from fish, so it is neither vegan nor vegetarian. Collagen is found only in animal tissue. Products sold as "vegan collagen" or "collagen boosters" contain no collagen; they provide nutrients the body uses to make its own, such as vitamin C, which contributes to normal collagen formation.

Frequently asked questions

Is it safe to take marine collagen every day?

Marine collagen supplements are designed for daily use, and in clinical trials collagen supplements have generally been well tolerated. Keep to the label dose and check the other ingredients if you take medicines.

Can I take marine collagen with other supplements?

Usually, yes. Check labels so you do not double up on ingredients such as vitamin C, zinc or CoQ10, and ask your doctor if you take regular medication.

Who should not take marine collagen?

People with a fish allergy, vegetarians and vegans. People who are pregnant or breastfeeding, or who take regular medicines such as blood thinners or diabetes medicines, should speak to their doctor first.

How long does marine collagen take to work?

Studies usually measure skin changes after 8–12 weeks of daily use, and results vary. Read more in how long it takes to see skin changes from supplements.

References

• Choi FD, Sung CT, Juhasz MLW, Mesinkovska NA. Oral collagen supplementation: a systematic review of dermatological applications. Journal of Drugs in Dermatology. 2019;18(1):9–16. jddonline.com
• Harvard T.H. Chan School of Public Health, The Nutrition Source. Collagen. nutritionsource.hsph.harvard.edu
• Hamada Y, Nagashima Y, Shiomi K. Identification of collagen as a new fish allergen. Bioscience, Biotechnology, and Biochemistry. 2001;65(2):285–291. doi:10.1271/bbb.65.285
• Fujimoto W, Fukuda M, Yokooji T, et al. Anaphylaxis provoked by ingestion of hydrolyzed fish collagen probably induced by epicutaneous sensitization. Allergology International. 2016;65(4):474–476. doi:10.1016/j.alit.2016.03.012
• Cammilleri G, Tortorici M, Pantano L, et al. Toxic metals and metalloids in collagen supplements of fish and jellyfish origin: risk assessment for daily intake. Open Medicine. 2025;20(1):20251141. doi:10.1515/med-2025-1141
• Myung SK, Park Y. Effects of collagen supplements on skin aging: a systematic review and meta-analysis of randomized controlled trials. The American Journal of Medicine. 2025. doi:10.1016/j.amjmed.2025.04.034
• National Center for Complementary and Integrative Health (NIH). Coenzyme Q10. nccih.nih.gov
• NIH Office of Dietary Supplements. Vitamin E: Fact Sheet for Health Professionals. ods.od.nih.gov
• Bhardwaj RK, Glaeser H, Becquemont L, et al. Piperine, a major constituent of black pepper, inhibits human P-glycoprotein and CYP3A4. Journal of Pharmacology and Experimental Therapeutics. 2002;302(2):645–650. doi:10.1124/jpet.102.034728

This article is for general education and is not medical advice. Food supplements are not intended to diagnose, treat, cure or prevent any disease. Consult a qualified healthcare professional before starting any supplement, particularly if you are pregnant, breastfeeding, have a medical condition or take medication.