Can Collagen Powder Cause Constipation? What Is Known
Can collagen powder cause constipation? It has been reported once in the trials we found: 2 of 39 people in one 16-week trial, taking a collagen hydrolysate, had moderate constipation that lasted one day and did not come back when the collagen was given again. Most other collagen trials and reviews report no constipation at all. No trial was built to measure it, so the true rate is not known.
This page describes what published studies and the NIH report. It is not medical advice.
Short answer
- Has anyone become constipated on collagen in a trial?
- Yes, 2 of 39 people on one collagen hydrolysate in a pressure ulcer trial. It lasted one day and did not return on re-challenge.
- Is it common?
- Not in the record we found. A 2022 review said none of the studies it covered reported constipation, in either the collagen or the control groups.
- Does the NIH list collagen as a cause of constipation?
- No. Collagen is not named anywhere on the NIH (NIDDK) page of constipation causes, or in its list of supplements that can make it worse.
Sources: Collagen hydrolysates and pressure ulcer trial, 2018 (Europe PMC); Collagen supplements for aging and wrinkles review, 2022 (Europe PMC); NIDDK (NIH): Symptoms and Causes of Constipation
Every constipation report we found, in one table
Searches of PubMed and Europe PMC for collagen with constipation or bloating found two trials that reported constipation. Only one of them saw it in people taking collagen.
| Source | What people took | Constipation reported | Notes |
|---|---|---|---|
| Pressure ulcer trial, 2018 | Collagen hydrolysate CH-a, twice daily, 10 g a day, 16 weeks | 2 of 39 people, moderate | Lasted one day; did not return on re-challenge; 1 person also had mild diarrhea |
| Calcium and vitamin D trial, 2020 | Group A: 5 g collagen peptides with calcium lactate and vitamin D3 | None | No adverse events in this group |
| Calcium and vitamin D trial, 2020 | Group B: calcium carbonate chewable with vitamin D3, no collagen | Yes, among 3 people (14%) with minor events | Events were constipation, indigestion and biliary colic |
| Collagen skin review, 2022 | Collagen in the skin studies it covered | None | Also no vomiting, diarrhea or nausea in treatment or control groups |
Disclaimer: these are the amounts used in research, not a recommendation. Decisions about what to take belong with a licensed clinician who knows your history.
So the whole collagen-group record, in the sources we found, is two people for one day. That is enough to say it can happen, and not enough to say how often.
Sources: Collagen hydrolysates and pressure ulcer trial, 2018 (Europe PMC); Calcium and vitamin D with or without collagen peptides trial, 2020 (Europe PMC); Collagen supplements for aging and wrinkles review, 2022 (Europe PMC)
What happened in the trial that reported constipation?
In a randomized, double-blind, placebo-controlled trial of collagen hydrolysates for pressure ulcer healing, 2 of the 39 people given the product called CH-a had moderate constipation, and 1 had mild diarrhea.
The trial report gives the schedule as:
Twice daily, 10 g per day in total, for 16 weeks
Disclaimer: these are the amounts used in research, not a recommendation. Decisions about what to take belong with a licensed clinician who knows your history.
The authors wrote that all of these adverse events may have been caused by the treatment or the placebo. They lasted only one day and cleared with other medicine. When the product was given again, none of the events came back. So the authors did not pin the events on the product, and restarting it did not bring them back.
Sources: Collagen hydrolysates and pressure ulcer trial, 2018 (Europe PMC)
Why the calcium trial points away from collagen
In a trial in postmenopausal women with low bone density, the constipation happened in the group that did not take collagen.
The trial report lists the two daily products as:
- Group A: a sachet with 5 g collagen peptides, 3.6 g calcium lactate (500 mg elemental calcium) and 400 IU vitamin D3
- Group B: a chewable tablet with 1.25 g calcium carbonate (500 mg elemental calcium) and 400 IU vitamin D3
Disclaimer: these are the amounts used in research, not a recommendation. Decisions about what to take belong with a licensed clinician who knows your history.
There were no serious adverse events. Three people (14%) in group B reported minor events: constipation, indigestion and biliary colic. Group A, the collagen group, had better compliance and no adverse events. The difference between groups was not statistically clear (p=0.083), so it does not prove collagen protects against constipation. It does show that in this trial the problem came from the calcium carbonate arm.
Sources: Calcium and vitamin D with or without collagen peptides trial, 2020 (Europe PMC)
What do the reviews of collagen trials say?
Three reviews of collagen for skin found it well tolerated, but the trials behind them have quality problems.
- A 2019 systematic review concluded collagen supplementation is generally safe with no reported adverse events.
- A 2022 review said no side effects such as vomiting, diarrhea, nausea or constipation were reported in the treatment or control groups of any of its studies.
- A 2026 systematic review of randomized trials found hydrolyzed collagen generally well tolerated, with a low rate of adverse events. It also rated most of the trials it included as having a high risk of bias.
These were skin trials. They reported stomach effects only as side notes, so a mild change in bowel habits might not have been recorded. For the same pattern on the skin side, see can collagen cause breakouts.
Sources: Oral collagen dermatology review, 2019 (PubMed); Collagen supplements for aging and wrinkles review, 2022 (Europe PMC); Hydrolyzed collagen skin health systematic review, 2026 (PubMed)
Does collagen powder affect your bowels?
Bowel effects showed up in only one trial of people taking collagen, and one small study reported less bloating rather than more.
A 2022 two-phase study in healthy women used:
20 g of collagen peptides a day
Disclaimer: these are the amounts used in research, not a recommendation. Decisions about what to take belong with a licensed clinician who knows your history.
The authors concluded this may reduce bloating and improve mild digestive symptoms in otherwise healthy women. The result rests on a small group: of the 40 women recruited for phase 2, only 14 (35%) completed the full course. Treat it as a hint, not proof.
Sources: Collagen peptide and digestive symptoms study, 2022 (PubMed)
What is the downside of taking collagen powder?
In the trials, reported side effects were few, and some were rated moderate rather than mild. The clearest risk in our sources is allergy to the source animal, plus the weak quality of much of the research.
A 2020 case report found gummy tablets containing fish collagen caused anaphylaxis, a severe allergic reaction, in a child. The authors wrote that the case confirms fish collagen can cause anaphylaxis in children with fish allergies. Check what animal a product comes from if allergy is a concern.
The other downside is what the research cannot tell you. The 2026 review rated most of the skin-health collagen trials it included at high risk of bias. A small 2022 study did set out to explore digestive effects such as bloating, but it was uncontrolled, and the true rate of constipation is still not known. If a product also lists added minerals, note that the NIDDK names antacids containing aluminum and calcium among medicines and supplements that can make constipation worse; that line is about antacids, not collagen.
Sources: Fish collagen gummy anaphylaxis case, 2020 (PubMed); Hydrolyzed collagen skin health systematic review, 2026 (PubMed); NIDDK (NIH): Symptoms and Causes of Constipation
How to avoid constipation while taking collagen
No study tested ways to avoid constipation with collagen. Everything in this section is general constipation information from the NIH, not advice about collagen.
The NIH digestive institute (NIDDK) says constipation may mean fewer than three bowel movements a week; stools that are hard, dry or lumpy; stools that are hard or painful to pass; or a feeling that not all stool has passed. About 16 out of 100 US adults have symptoms of constipation, so it is common with or without any supplement.
The NIDDK lists causes that include not eating enough fiber, not drinking enough liquids or dehydration, and not getting enough physical activity. Its diet page says to eat enough fiber and drink plenty of liquids to help the fiber work better.
Because constipation is this common, a new supplement and a bout of constipation can line up by chance. If constipation starts after any new supplement, a clinician can help sort out whether it is the product or something else on that list.
Sources: NIDDK (NIH): Definition and Facts for Constipation; NIDDK (NIH): Symptoms and Causes of Constipation; NIDDK (NIH): Eating, Diet and Nutrition for Constipation
What are the signs of too much collagen?
No official or research source we found defines signs of too much collagen, and no trial we read tested high doses to find a limit. The amounts in the trials on this page were 5 g, 10 g and 20 g a day, and the only bowel events in a collagen group came at 10 g. For the calories in collagen-type powder, using gelatin as a stand-in, see does collagen break a fast.
Sources: Calcium and vitamin D with or without collagen peptides trial, 2020 (Europe PMC); Collagen hydrolysates and pressure ulcer trial, 2018 (Europe PMC); Collagen peptide and digestive symptoms study, 2022 (PubMed)
Common questions
Does collagen powder affect your bowels?+
Only in one trial we found. In that 16-week trial, 2 of 39 people on one collagen hydrolysate had moderate constipation and 1 had mild diarrhea, each lasting one day. A small 2022 study of 20 g a day reported less bloating and milder digestive symptoms.
What is the downside of taking collagen powder?+
In the trials we found, side effects were few, and some were rated moderate rather than mild. The clearest risk is allergy: a 2020 case report confirmed that fish collagen can cause anaphylaxis in children with fish allergy. A 2026 review also rated most of the skin-health collagen trials it included at high risk of bias.
How to avoid constipation while taking collagen?+
No study tested this for collagen. As general advice for constipation, not about collagen, the NIH says to eat enough fiber and drink plenty of liquids to help the fiber work better.
What are the signs of too much collagen?+
No official or research source we found defines signs of too much collagen, and no trial we read tested high doses to find a limit.
Can collagen powder cause bloating?+
We found no trial reporting bloating as a side effect. One 2022 study found 20 g a day may reduce bloating in healthy women, but only 14 of the 40 who started finished the full course.
Is constipation from collagen common?+
Not in the record we found. Only one trial reported it in a collagen group: 2 of 39 people. A 2022 review said no constipation was reported in the treatment or control groups of the studies it covered. No trial was designed to measure constipation.
Sources: Collagen hydrolysates and pressure ulcer trial, 2018 (Europe PMC); Collagen peptide and digestive symptoms study, 2022 (PubMed); Fish collagen gummy anaphylaxis case, 2020 (PubMed); NIDDK (NIH): Eating, Diet and Nutrition for Constipation; Collagen supplements for aging and wrinkles review, 2022 (Europe PMC); Hydrolyzed collagen skin health systematic review, 2026 (PubMed)
Related reading
This guide is for education only and is not medical advice. It describes what published studies and NIH pages report about collagen supplements and constipation. Talk to a licensed clinician about your own symptoms.