Collagen supplements containing collagen hydrolysate, collagen peptides and similar ingredients appear to be generally safe and well-tolerated. However, some people may experience mild side effects, ranging from gastrointestinal symptoms to skin rashes. Rarely, liver abnormalities have been reported, and people who are allergic to certain sources of collagen, such as fish, or who are allergic to sulfites, should not take collagen products containing these ingredients. Despite some concerns, there is no evidence that taking collagen supplements increases the risk of breast cancer or breast cancer recurrence. For more information, see the Concerns and Cautions section of the Collagen Supplements Review, which also includes our tests and Top Picks among products.
People with kidney disease or who are on dialysis should consult with their physician before consuming bone broth as a source of collagen, as some bone broths contain high amounts of sodium and potassium.