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Collagen side effects are usually mild. In clinical trials the most commonly reported problems were digestive, such as nausea or diarrhea, and a 2023 meta-analysis found no significant difference in adverse events between collagen and placebo, though it rated that evidence very low quality. The bigger questions depend on the person: allergy to the source animal (fish, egg or, for people with alpha-gal syndrome, beef or pork), the calories and protein a serving adds, a possible rise in urinary oxalate for people prone to kidney stones, and false lab results from biotin in some collagen blends. Safety in pregnancy has not been well studied.
Peptide Labs sells Vital Proteins Collagen Peptides, and we quote its label below. This article is general information, not medical advice. For what collagen peptides are, see hydrolyzed collagen explained.
Key Takeaways
- Collagen appears well tolerated; digestive complaints are the most commonly reported issue.
- Allergy risk follows the source: fish, egg, and beef or pork gelatin for alpha-gal syndrome.
- A serving of the Vital Proteins powder adds 70 calories and 18 grams of protein.
- Collagen raises urinary oxalate in lab studies; people with kidney stones should ask a clinician.
- Biotin, often added to beauty collagen blends, can distort some blood tests.
- Pregnancy and breastfeeding safety are unknown; ask a healthcare provider first.
Common collagen side effects
Most people who take collagen peptides report no problems. WebMD’s monograph describes collagen as seeming to be well tolerated, and a 2019 systematic review of 11 skin studies with 805 participants found no reported adverse events over trials lasting 4 to 24 weeks. A 2023 meta-analysis of four knee osteoarthritis trials with 507 people listed gastrointestinal disorders as the most common adverse events, including mild to moderate vomiting and diarrhea in one trial. The overall risk was not significantly different from placebo, but the result was borderline and the evidence was rated very low quality, so a small effect cannot be ruled out.
Collagen powders are protein, and a large scoop can feel heavy for some people. Flavored products may also contain sweeteners, sugar alcohols or added ingredients that cause their own digestive upset, so check the full label.
| Concern | What the evidence shows | Who should take note |
|---|---|---|
| Digestive upset | Most common complaint in trials; not significantly above placebo (very low quality evidence) | Anyone starting a new powder |
| Allergic reaction | Fish collagen can be an allergen; beef or pork gelatin can affect some people with alpha-gal syndrome | People with fish, egg or red meat allergies |
| Calories and protein | 70 calories and 18 g protein per Vital Proteins serving | People counting calories or told to limit protein |
| Urinary oxalate | Rose after gelatin in a small study of healthy adults | People with a history of kidney stones |
| Biotin in blends | Can cause falsely high or low lab results, per the FDA | Anyone having blood tests |
| Pregnancy | Not known whether collagen is safe for a fetus | Pregnant or breastfeeding women |
Collagen allergies by source
Collagen is made from animal skin, bones, scales or membranes, and allergy risk follows the source. Fish is a major food allergen that must be declared on U.S. labels, and fish collagen itself can trigger reactions: in a 2020 study, 21 of 101 fish-allergic patients had allergy antibodies to fish collagen, and a case report described a severe reaction in a child to gummies made with fish collagen. Eggshell membrane products, which contain several collagen types, matter for people with egg allergy.
Bovine products raise a different issue. The CDC lists gelatin made from beef or pork among the products that some people with alpha-gal syndrome, a red meat allergy linked to tick bites, react to, although not everyone does. The CDC does not mention collagen peptides specifically, but they are a closely related ingredient from the same animals, so people with this condition should ask an allergist first. The Vital Proteins label also states that the powder is made in a facility that processes milk and fish, and the largest size adds tree nuts. Our marine vs bovine collagen guide compares sources in more detail.
Does collagen make you gain weight?
Collagen does not have a known effect on body weight beyond its calories, which count like those of any other food. A 20 gram serving of unflavored Vital Proteins Collagen Peptides provides 70 calories and 18 grams of protein, with 0 grams of sugar on the smaller canisters. Adding it every day without adjusting anything else adds those calories, and a flavored product or a sweetened coffee drink adds more. The label itself says the powder is a food supplement only and not for weight reduction.
Collagen also should not replace regular protein. It lacks tryptophan, one of the essential amino acids, so it is an incomplete protein, and the Vital Proteins label says it should not replace dietary protein. People who have been told to limit protein, for example because of kidney disease, should count collagen toward that limit and check with their clinician.
Kidney stones and oxalate
Collagen is rich in hydroxyproline, an amino acid the body can break down into oxalate, a component of the most common type of kidney stone. In a 2006 study in Kidney International, 10 healthy adults ate controlled diets with gelatin or whey protein. Urinary oxalate was 43% higher on the gelatin diet, and changes appeared with larger single amounts but not the smallest ones tested. The study did not measure stones, used gelatin rather than modern collagen peptides and involved people without a stone history. The evidence is limited, but people who have had calcium oxalate stones or have a condition that raises oxalate should talk to their clinician before using collagen daily.
Collagen and biotin: the lab test problem
Many hair, skin and nail collagen blends add biotin, also called vitamin B7. The FDA issued safety communications in 2017 and 2019 warning that high biotin intake can interfere with certain lab tests and give falsely high or falsely low results. Its main concern is falsely low troponin results, a test used to help diagnose heart attacks, and it notes that some supplements marketed for hair, skin and nails contain biotin at up to 650 times the recommended daily intake. If your collagen product lists biotin, tell your healthcare provider and the lab before any blood test. The unflavored Vital Proteins powder we sell lists collagen peptides as its only ingredient.
Heavy metals and quality testing
Any animal-derived supplement can carry trace contaminants. A 2025 Italian study of fish and jellyfish collagen supplements found arsenic most often and mercury in 12% of samples, with levels varying by brand, although none exceeded European Union limits. Harvard’s Nutrition Source mentions a study that found low levels of lead and cadmium in collagen products, and notes that most collagen research is funded by related industries. Because the FDA does not review supplements before sale, look for a named independent testing program or a certificate of analysis.
Is collagen in coffee safe?
Adding collagen peptides to coffee is common and the Vital Proteins label says the powder dissolves in hot and cold liquids. Hydrolyzed collagen is made by heating collagen until its triple-helix structure unwinds and then breaking it into small peptides with enzymes, so it has already been exposed to heat during manufacturing. We found no study testing whether coffee changes how collagen is absorbed. The main things to watch are the extra calories from sweetened drinks and your total caffeine intake. For timing questions, see our collagen timing guide.
Who should talk to a clinician first
- People who are pregnant or breastfeeding: WebMD states it is not known whether collagen could affect pregnancy or pass into breast milk, and the Vital Proteins label advises consulting a healthcare practitioner.
- People with fish, egg or shellfish allergies, or alpha-gal syndrome.
- People with a history of kidney stones or kidney disease.
- Anyone taking medicines or managing a health condition, as the label advises; interactions between collagen and medicines are not fully understood.
- Anyone using a collagen blend with biotin who has upcoming blood tests.
Frequently Asked Questions
What are the side effects of collagen?
Collagen appears well tolerated. Digestive complaints such as nausea or diarrhea were the most commonly reported problems in trials, at rates not significantly different from placebo.
Is collagen safe to take every day?
Trials of up to about six months reported few problems in healthy adults, but long-term safety data are limited. Follow the label and ask a healthcare provider, especially if you have a medical condition.
Does collagen make you gain weight?
Not by itself. It adds calories like any food: 70 calories and 18 grams of protein per serving of unflavored Vital Proteins Collagen Peptides.
Can you take collagen and biotin together?
Many products combine them. The FDA warns that biotin can cause false lab results, including falsely low troponin, so tell your provider and the lab if you take biotin.
Can collagen cause kidney stones?
It has not been shown to. Gelatin raised urinary oxalate in a small study of healthy adults, so people with a history of kidney stones should ask their clinician.
Can I put collagen in hot coffee?
Yes. Collagen peptides dissolve in hot liquids and are made using heat, and no study shows coffee changes absorption. Watch added sugar and caffeine.
Questions about the product? Contact us. Follow the label and ask a healthcare provider before starting any supplement. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
Last reviewed September 2026.
Related guides: Best Time to Take Collagen: Timing, Evidence and Collagen vs Protein Powder, Marine Collagen vs Bovine Collagen: Collagen Types, Sources and Safety, Hydrolyzed Collagen: What It Is, How It Is Made and How It Differs From Gelatin, Collagen Peptides Benefits: What Skin, Joint, Bone and Muscle Studies Show, Biotin Side Effects, Benefits and the Lab Test Problem.