Hair falling out and nails breaking: which tests to get

What it is and why it matters

Hair has started falling out and nails are splitting? Most often there is an explanation, and the list of tests is short.

• Shedding after an illness, stress, childbirth or a diet is often reversible
• Brittle nails are far from always a lack of vitamins
• Below: which tests to take and when to see a doctor

Why hair doesn’t fall out right away

A hair grows for years, then “rests” for a few months and falls out. An illness, childbirth, sudden weight loss or emotional strain send many hairs to rest at once.

• That’s why hair sheds 2–4 months after the event, and sooner after COVID
• Think back: was there a strict diet 2–4 months before the shedding?
• Hair often grows back, but a long-lasting form also happens

The basic set of tests

The set of tests for hair loss is short. Zinc is added to it when there’s a reason.

• A complete blood count — to check for anemia
• Iron stores, and together with them a test for inflammation
• The hormone used to check the thyroid, and vitamin D

Iron stores

In women whose hair loss leaves no scars on the skin, iron stores are on average lower than in women without hair loss.

• Inflammation inflates the iron-store test — so a test for inflammation is taken alongside it
• How much iron in store hair needs has not been firmly established
• The numbers you come across are practice guides, not proven cut-offs

Honestly. Whether topping up iron helps hair is not yet known. Studies show a link, not proof of a cause.

Vitamin D and zinc

In some studies, vitamin D (in women with certain types of hair loss) and zinc in people with hair loss were on average lower than in those without it.

• This is a link, not a proven cause
• No evidence was found that low zinc causes hair loss
• The normal ranges for both tests are set by the lab

Important. Don’t take iron, zinc or “hair vitamins” blindly: too many supplements can themselves cause hair loss. Without a proven shortage, they are not recommended.

Biotin can distort test results

Biotin can distort blood tests: some results come out falsely high, others falsely low.

• Among the tests checked are the very ones used for hair loss: thyroid, vitamin D, iron stores
• Taking biotin or “hair vitamins”? Tell your doctor before the blood draw

Female-pattern thinning

Hair thins in the middle of the head, while the hairline above the forehead stays. If male hormones are normal, this kind of thinning doesn’t point to an excess of them.

• Checking male hormones is advised with any such thinning
• When there’s a reason, a test for one more hormone, prolactin, is added
• Irregular periods or acne are a reason to discuss hormones and ovaries with a doctor

Brittle nails

Brittle, splitting nails are not rare, more often in older women. And it’s far from always a lack of vitamins.

• It can happen without an obvious cause, or because of an infection, a nail disease or a whole-body illness
• Other causes are injuries and drying out of the nail, so the cause is treated first
• For the nail itself, moisturizers and strengthening coatings can be considered

Who should see a doctor first

It makes sense to see an endocrinologist if the thinning comes with irregular periods, acne or hair growth on the face and body, and also if the thyroid test is out of range.

• Hair falls out in patches, round smooth spots — see a dermatologist
• The skin where hair fell out is red, flaky, painful or shiny — don’t put off the dermatologist
• In clumps, very fast or for longer than six months — see a dermatologist, don’t wait for it to pass on its own

Important. A dark lengthwise stripe on a nail, pain or the nail lifting off is a reason to see a dermatologist.

In one sentence

Recall what happened 2–4 months before the shedding, take the basic tests and tell your doctor about biotin. Shedding after an illness, stress or childbirth is often reversible, though it can also drag on.