Over 80% of men and Christopher Caldwellalmost 50% of women experience significant hair loss at some point in their life, according to NYU Langone Health. Enter, the vitamin and supplement industry, which advertises hair growth vitamins as the answer to your problems.

Unfortunately, health experts say it's not always quite as simple as popping a pill to regrow your locks.

"Hair loss isn't necessarily due to a vitamin deficiency and taking vitamins doesn’t guarantee hair growth," Washington, D.C.-based dietitian Caroline Thomason, R.D., tells USA TODAY. 

When are vitamins the answer to hair growth? Health experts explain.

What vitamin deficiency causes hair loss?

As Thomason noted, hair loss can happen for a number of reasons. It doesn't necessarily mean you're deficient in any vitamins.

When it comes to men, androgenetic alopecia (male or female pattern baldness) is to blame for about 95% of hair loss cases, according to NYU Langone. That probability drops down to about 40% for women. Other common causes can include genetics, hormonal imbalances, stress, medications or medical conditions, Thomason says.

If vitamin deficiency is the reason for your hair loss, it's likely because of low levels of biotin and/or vitamin D, board-certified dermatologist Hadley King, M.D., tells USA TODAY.

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What vitamins are good for hair growth? 

Again, taking vitamins likely won't help your hair will grow if your hair loss wasn't triggered by any vitamin deficiencies to begin with.

If you're experiencing hair loss, Thomason says your first step should be consulting a healthcare provider. They can conduct a blood test to determine if you have a deficiency that could be causing it. If that's the case, then taking vitamins may in fact be the right course of action.

King highlights biotin, fat-soluble vitamins A, D, and E along with vitamin C as ones that have been shown to help prevent hair loss. But don't start taking vitamins on your own without talking to a doctor, as other health complications can arise if you wind up boosting those vitamin levels past the safe limit, or if they react negatively with another health condition or medication.

Taking too much of vitamin A and selinium can actually further contribute to hair loss, according to Harvard Health. And too much biotin, which is found in most skin, hair and nail supplements, can negatively interfere with some thyroid and hormone lab tests.

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If vitamin deficiency isn't the cause of your hair loss, Thomason suggests making sure you're "eating enough food, meeting your protein requirements, sleeping consistently and managing stress levels" to prevent hair loss and support its growth.