Do Hair Growth Vitamins and Biotin Work?

The bottle on the shelf has a glowing woman on the label and a promise in capital letters. Your hairbrush has more in it than it used to. You’re holding the bottle, and the pitch is easy to follow: $30, a few weeks, thicker hair.

What biotin does

Biotin is a B vitamin. Cleveland Clinic¹ says it helps produce keratin, the protein that makes up hair, skin and nails, and that a deficiency can cause hair loss. That’s where the marketing comes from.

The jump from “deficiency causes hair loss” to “extra biotin grows more hair” is the part the research doesn’t support yet. Cleveland Clinic¹ points to a 2012 study in which women’s hair thickness improved after taking a multivitamin that contained biotin, and notes that other ingredients may have contributed.

Cleveland Clinic¹ gives the daily amount adults need as 30 micrograms, and lists food sources: beef liver at 30.8 micrograms, eggs at 10, salmon at 5, pork chops at 3.8, plus sweet potatoes, almonds and broccoli.

What the AAD says

The AAD² is the clearest on this. If your dermatologist suspects a disease, vitamin deficiency, hormone imbalance or infection behind your hair loss, you may need a blood test or scalp biopsy. Then comes the rule: you should only take biotin, iron or zinc when your blood test shows you have a deficiency. If your levels are normal, a supplement can be harmful.

The AAD² gives an example. Too much iron can cause iron poisoning, with early signs of stomach pain and vomiting. And because a hair-loss supplement can push you past what you need of a nutrient, many dermatologists recommend a multivitamin instead.

The NHS³ lists iron deficiency among the causes of temporary hair loss, along with illness, stress, cancer treatment and weight loss. That’s a reason to find out your iron before you guess at it.

The lab-test problem

Cleveland Clinic¹ calls biotin exceedingly safe in reasonable amounts, though too much can cause stomach trouble, sleep problems or a rash. It also warns that biotin may interfere with certain common lab tests, so tell your doctor before testing.

The FDA⁴ is firmer. It says biotin, often found in dietary supplements, can significantly interfere with certain lab tests and cause incorrect results that may go undetected. It names troponin tests in particular, saying it has continued to receive reports that biotin caused falsely low troponin results.

That’s a reason to mention your supplements any time you have blood drawn, including at an emergency room.

What usually matters more

Cleveland Clinic¹ says hair loss can stem from underlying problems: endocrine disorders, anemia, digestive problems or poor nutrition. Dermatologists look at diet, exercise, family history, medicines and bloodwork. The NHS³ says we lose 50 to 100 hairs a day, often without noticing, and some hair loss, like pattern baldness, runs in families.

Which means the first question isn’t which bottle. It’s why. Our article on why your hair is thinning separates the two big patterns, and chin hairs covers the opposite problem.

The play

Try this: ask before you add

Write down every supplement you take now, with the dose from the label.

Bring that list to your doctor or dermatologist and ask whether a blood test for iron or other deficiencies makes sense for your hair loss.

Tell whoever draws your blood about any biotin, because of the lab-test problem.

When to get checked

Don’t wait if

1. Urgent

   If you’ve taken too much iron and have stomach pain and vomiting, get medical help right away. The AAD² lists those as early signs of iron poisoning.

The NHS³ says to see a GP if you’re worried about your hair loss, and to get professional advice before you visit commercial hair clinics, since a GP can help identify the cause. The AAD² recommends a board-certified dermatologist for an accurate diagnosis.

Book an appointment if any of these fit:

• Your hair is thinning, shedding or falling out in patches
• You’ve been taking a hair supplement for months and nothing has changed
• You take biotin and have blood tests coming up
• You’re considering taking iron or zinc on your own
• You’re pregnant or taking medicines and want to add a supplement

The bottle can stay on the shelf. Start with the blood test, and let the answer decide what goes in the cart.