For most people, collagen is healthy to take. The vast majority of those who supplement with it experience zero side effects. The only known side effect of collagen in healthy people is digestive discomfort, and that’s still pretty rare (1).

But if you’re living with a complex health issue like kidney disease, there are three very important facts to consider before taking a collagen supplement. Read on to find out whether collagen and kidneys are a safe match…

Concerns over collagen supplements and kidney health break down into a few different key considerations.

1. Collagen and Creatinine

For starters, it’s worth examining the connection between collagen and creatinine.

Creatinine is a waste product that comes from a compound in the body called creatine. Your kidneys filter creatinine (and other waste) out of the blood, which is ultimately excreted in the urine.

Because creatinine serves as a key indicator of how well someone’s kidneys are working at filtering waste out of the body, those living with kidney disease closely monitor creatinine levels in their blood. When creatinine levels are higher than normal, it could mean that a patient has kidney disease, or that their kidney disease is getting worse.

This is where collagen comes in…

Collagen is loaded with amino acids that help your body function at its best. Normally, this would be considered a positive, but it can get complicated for people with kidney disease. Glycine and proline, some of the more common amino acids in collagen, are used by the body to make creatine, which ultimately converts to creatinine (2).

While there is a lot yet to be researched, this leads to concerns about a connection between collagen supplements and potential creatinine increases for kidney disease patients.

2. Collagen and Kidney Stones

Another amino acid in collagen is hydroxyproline, which exists in all animal proteins (3). The body converts hydroxyproline into oxalate—a naturally-occurring compound that’s found in plants. With the help of the kidneys, the body excretes oxalate through urine (4).

If one consumes too much of any food product or supplement that has high levels of hydroxyproline, the body may excrete excess oxalate. This increases your risk for the most common type of kidney stone: Calcium oxalate kidney stones (5, 6).

For some people, kidney stones may pose a risk for kidney disease (7). Because of this, people who are prone to kidney stones should avoid collagen supplements, especially those with primary hyperoxaluria, a genetic disorder that increases your kidney stone risk (8).

If you don’t have an unusually high risk of kidney stones, however, collagen is usually considered safe.

3. There’s a Lot We Don’t Know Yet, So Talk to Your Doctor

If your kidneys are healthy and not at risk, you are fine to take collagen unless your doctor says otherwise. Collagen is not linked to an increased risk of kidney stones or other kidney issues in people with healthy kidneys.

If you have kidney disease or regularly get kidney stones, there’s a chance that collagen could increase your risk of these health issues. There’s a lot we still don’t know, and there’s a lot left to learn from the research that does exist…

For example, one study indicates that the body’s collagen levels may increase with the progress of kidney fibrosis (the formation of scar tissue in the kidneys that occurs in virtually all types of kidney disease). The study also found that decreasing the amount of collagen in the body may slow that process (9).

Another study found that collagen levels may serve as an important marker of the progress of this fibrosis (10).

When it comes to kidney stones, some research indicates that reducing the hydroxyproline in your body (and thus reducing your collagen intake) may not even be necessary for reducing your risk, as long as you increase your calcium intake (11, 12).

All of this to say: It’s currently unclear whether collagen poses a direct risk to people with kidney-related health issues when taken in regular doses. It’s complicated! But when it comes to your health, erring on the side of caution is always a good idea. Unless your doctor gives the okay, it’s better for kidney disease patients to curb their collagen consumption.

Collagen is safe and beneficial for the vast majority of healthy people. Some early indications point to a potential risk for people with kidney disease or with a high risk of kidney stones. If you have any concerns about your risk level, talk to a health provider before making collagen a part of your routine.