If hair growth is a top concern for you, then you probably have considered taking either a collagen or biotin supplement (or both!). These ingredients are everywhere, and it’s nearly impossible to scroll through any social feed without seeing personal anecdotes from people who swear by their supposed hair-growing abilities.

But with so much conflicting information out there, it can be hard to figure out which supplement would actually work best (if at all) for you and your hair needs. So, to settle the debate between collagen and biotin, we turned to the experts. See what they had to say below.

How collagen works for hair growth

Collagen plays a vital role in many parts of the body, including healthy hair growth. As Morgan Rabach, MD, board-certified dermatologist at Rabach Aesthetics, explains it, when our dermal collagen is healthy, hair follicles are better anchored in our scalp to grow. As we get older, our collagen levels decline, and our skin gets thinner. Dr. Rabach says this can then cause circulation to slow down, and hair becomes more prone to breakage and damage.

So, where do collagen supplements come into this? It’s believed they can support hair thickness through the skin-related benefits. New York City-based dermatologist Hadley King, MD, explains that studies show that collagen supplements, which are made of collagen peptides that are easier to absorb, and topical products are most proven to improve hydration and strengthen the skin barrier. Because collagen may help support scalp health, it is possible that it might also result in healthy hair growth, but Dr. King says evidence for this is still limited. “The jury is still out,” she says.

Those who have fish, shellfish, egg, or beef allergies should use caution when taking collagen supplements, as they are sometimes made from animal-derived ingredients. She also says that those with kidney disease, conditions that require protein restriction, or who are pregnant or breastfeeding should first consult with their healthcare provider to be extra safe. Other downsides include mild bloating, upset stomach, or an off-putting taste. So, something to think about before you start integrating collagen supplements into your routine.

How biotin works for hair growth

Biotin, also known as B7, is a well-known part of prenatal supplements, but that’s not its only use. Dr. King explains that because hair loss is a symptom of biotin deficiency, biotin is an ingredient that is often recommended to help with hair growth. Dr. Rabach says that it may help correct those deficiency-related hair problems and adds that she has patients who swear by biotin for hair thinning and brittle nails. But in reality, there’s actually more that needs to be studied.

“According to the NIH, there isn’t enough evidence to evaluate biotin’s effectiveness in the treatment of hair loss,” says Dr. King. “Additional research is needed to determine whether biotin supplements can improve skin, hair, and nail health in adults, [especially for those] who aren’t deficient in this vitamin.”

“True deficiencies are uncommon,” adds Dr. Rabach. “So you definitely don’t want to take this supplement and not get a medical workup, thinking that the supplement will help. Get a full workup by a doctor and a TricoTest to determine what hair supplements will work the best for you.

Also, be careful when taking biotin. Dr. King warns that it can interfere with certain lab results, including those for thyroid hormones, reproductive hormones, and cardiac tests. So be sure to keep your doctor in the loop.

Is collagen or biotin better for hair growth?

Technically, biotin has more scientific evidence than collagen when it comes to hair growth. But again, biotin is really only helpful when there is a biotin deficiency. Those who have brittle hair, strict dietary restrictions, nutritional deficiencies, or gastrointestinal absorption issues will have the most benefit from these supplements. “There is very small—or no likely—benefit for either supplement in a healthy person with a normal diet,” Dr. Rabach says.

And while you can take collagen and biotin supplements together, both experts say combining them won’t necessarily guarantee better results. “Hair loss is hormonal, stress- or thyroid-related, genetic, or [caused by] autoimmune [diseases],” she says. “[Supplements] alone in these cases are likely insufficient.”

Dr. King says that it’s actually topical minoxidil that people should turn to for hair growth—because it’s the most proven over-the-counter option that works for both men and women. (Although if you have pets, please be warned that it’s highly poisonous to them.) And something that all experts preach is to go see a doctor whenever you have questions. It’s always best to consult with a professional for a plan that will work best for you.

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