Skip to content
FORM

Hair loss: which blood tests are actually useful

Headshot of Dr. Nikola Topalovic, MD PhD
Medically reviewed by Dr. Nikola Topalovic, MD PhD · Last reviewed 4 September 2026

Most male hair loss is genetic and blood tests will not explain it. Testing earns its place for the minority of cases that are not — and those are the reversible ones.

What people notice

  • Diffuse thinning rather than a receding hairline or crown
  • Sudden increased shedding two to three months after an illness, surgery or stressful period
  • Hair loss alongside fatigue, cold intolerance or weight change
  • Loss of body hair as well as scalp hair
  • Brittle nails and dry skin at the same time

Symptoms overlap between causes. This list is a prompt to measure, not a diagnosis.

Markers worth measuring

Ferritin and iron studies
Low iron stores are a well-documented and correctable contributor to diffuse shedding, particularly with heavy training or blood donation.
TSH, free T4, free T3
Both underactive and overactive thyroid cause hair loss, and both are straightforward to identify.
Vitamin D
Involved in the hair follicle cycle; deficiency is common and easy to exclude.
Zinc and B12
Deficiency of either contributes to telogen effluvium, the diffuse shedding pattern.
DHT and testosterone
Context rather than diagnosis — pattern hair loss is driven by follicle sensitivity to DHT, not by an abnormal blood level.
Full blood count and CRP
Anaemia and systemic inflammation both show up as diffuse hair loss.
ANA and syphilis serology where indicated
Uncommon but genuine causes of hair loss that are cheap to exclude when the pattern fits.

Pattern first, bloods second. Androgenetic hair loss follows a recognisable pattern — temples and crown, gradual, usually with a family history — and blood levels in these men are typically normal, because the mechanism is follicle sensitivity to DHT rather than an excess of it. Measuring DHT in that setting rarely changes anything. Diffuse thinning across the whole scalp, or sudden shedding, is the pattern where bloods pay off.

The three-month lag. Telogen effluvium — the diffuse shedding that follows an illness, an operation, a crash diet, a fever or a period of severe stress — appears two to three months after the trigger. People routinely look for a cause in the wrong month. Iron, thyroid and vitamin D are the correctable contributors to check, and the shedding typically resolves once the trigger is addressed.

Interpreting ferritin for hair. Hair follicles appear to be sensitive to iron stores at levels above the threshold for anaemia, so a ferritin technically 'in range' can still be relevant. Read it with CRP, since inflammation inflates it, and with a full blood count.

What we do not claim. No blood test predicts whether hair will regrow, and FORM does not prescribe or supply any hair loss treatment. What the panel does is identify correctable contributors and rule out systemic causes so that a conversation with your own doctor or dermatologist is grounded.

FAQs

Is there a blood test for male pattern baldness?
No. It is a clinical diagnosis based on pattern and history. Blood levels of testosterone and DHT are usually normal, because the mechanism is follicle sensitivity.
Can low iron cause hair loss?
Low iron stores are an established contributor to diffuse shedding, and follicles may be affected at ferritin levels above the anaemia threshold.
Why did my hair start falling out months after being ill?
That delay is characteristic of telogen effluvium — the trigger pushes follicles into the resting phase and the shedding becomes visible two to three months later.
Should I test DHT?
It is context rather than a diagnosis. It can be worth having in a broad hormone panel, but a normal DHT does not exclude pattern hair loss and a high one does not confirm it.

Measure it properly, in one morning draw.

Compare panelsTesting by city

Related testing topics

Explore FORM

60-second quiz
Find your panel · 5 questions
Start quiz →