Hormone Tests for Hair Loss: What to Ask Your GP For
Which hormone tests should you ask for when your hair is falling out? The core panel is thyroid function (TSH and free T4), a full blood count, ferritin to check iron stores, vitamin D and B12. If your periods are irregular or you also have acne or new facial hair, add testosterone, SHBG, LH, FSH and prolactin. That short list catches most of the treatable causes.
Knowing what to ask for changes the appointment. Hair loss is easy for a busy ten minute consultation to file as cosmetic, and the tests that most often find something (thyroid and ferritin) are also the two most often skipped. This guide covers the panel, when in your cycle to have it done, how to prepare so the results are not distorted, what a normal result does and does not rule out, and which private tests are not worth your money.
Key takeaways
- Ask for thyroid function, full blood count, ferritin, vitamin D and B12 as the baseline. They are cheap, routine, and find treatable causes.
- FSH and LH need to be taken on days 2 to 5 of your cycle to mean anything. Booking on the wrong day wastes the test.
- Take prolactin and testosterone in the morning, rested. Both vary through the day and with stress.
- High dose biotin supplements distort thyroid and other immunoassay results. Tell the clinic and ask how long to stop taking it beforehand.
- Bring a list of every medication and supplement. Several common drugs cause shedding, and that is quicker to spot than to test for.
- A normal panel does not mean nothing is wrong. Pattern hair loss is diagnosed by examining the scalp, not by blood.
- Skip saliva hormone kits, hair mineral analysis and IgG food intolerance panels. No clinician will act on them.
Which blood tests are worth asking for when hair is falling out?
The useful tests fall into two groups: a baseline panel that is reasonable for anyone with unexplained shedding, and a second tier that is only worth doing if your symptoms point that way. Asking for the baseline is straightforward. Asking for the second tier works better when you can say why.
| Test | Why it matters for hair | Timing and preparation |
|---|---|---|
|
TSH and free T4 Baseline |
Both underactive and overactive thyroid cause diffuse shedding, and both are very treatable | Any time of day. Stop high dose biotin first, it distorts the result |
|
Full blood count Baseline |
Detects anaemia, which commonly sits behind diffuse shedding in women | Any time. No preparation needed |
|
Ferritin Baseline, the one most often missed |
Iron stores can be low enough to affect hair while a full blood count still looks normal | Any time, but ferritin rises during infection, so retest if you were unwell |
|
Vitamin D Baseline |
Deficiency is very common in the UK and is associated with several hair loss conditions | Any time. Note the season, levels are lower in winter |
|
Vitamin B12 and folate Baseline |
Deficiency affects cell turnover, and is more likely on a vegan diet or with certain medications | Any time. Mention any B12 supplement you take |
|
Testosterone and SHBG If acne, facial hair or irregular periods |
Raised androgens point towards PCOS or another androgen excess cause | Morning, ideally before 10am. Levels fall through the day |
|
LH and FSH If periods are irregular or absent |
Helps separate PCOS from early ovarian insufficiency and other causes | Days 2 to 5 of your cycle. Outside that window the numbers are hard to read |
|
Prolactin If missed periods or nipple discharge |
Raised prolactin has specific treatable causes, including some medications | Morning, rested, no exercise or nipple stimulation beforehand. Often repeated if borderline |
|
Coeliac screen If iron is low with digestive symptoms |
Undiagnosed coeliac disease is a classic cause of stubbornly low iron | Must be eating gluten for the test to be valid. Do not cut it out first |
|
Zinc Occasionally, in specific cases |
Genuine deficiency affects hair, but it is much rarer than the internet suggests | Not routinely offered. Reasonable to ask about with restricted diets or gut disease |
Why will my GP not just test all my hormones?
NHS testing is symptom led rather than exploratory, because broad hormone panels in people without matching symptoms produce a high rate of borderline results that mean nothing and lead to unnecessary worry and follow up. It is a sensible approach in general, and it can feel dismissive when the thing you are worried about is your hair.
The way around it is to bring the symptoms, not just the request. Saying "my hair has been shedding since April, I am always cold and I have gained weight without changing anything" makes thyroid testing obviously appropriate. Saying "I would like my hormones checked" does not point anywhere. If you are not sure which cluster describes you, our companion guide to working out which hormone is causing your hair loss sets the patterns out side by side so you can name yours.
How should you prepare for the blood test?
Preparation matters more than most people realise, because several of these results move with the time of day, the point in your cycle, recent illness and what you have been taking. A distorted result either sends you down the wrong path or leaves you repeating the test.
- Book a morning slot if you are having testosterone or prolactin done. Both are higher early and fall through the day.
- Check your cycle day before booking, if LH and FSH are on the list. Days 2 to 5 counting from the first day of proper bleeding.
- Ask about biotin. High dose biotin, the kind in hair and nail supplements, interferes with a range of laboratory immunoassays including thyroid tests. Tell the clinic what you take and ask how long to stop it beforehand.
- Wait if you have been ill. Ferritin rises with inflammation, so a recent infection can mask low iron stores entirely.
- Keep eating gluten until after a coeliac screen. Cutting it out first invalidates the test.
- Bring a written list of every prescription, over the counter medicine and supplement, with doses.
- Do not exercise hard beforehand on a prolactin morning, and try to arrive without rushing.
What should you take to the appointment?
Ten minutes goes quickly, and hair loss is a hard thing to describe under pressure. Turning up with three specific pieces of information makes the difference between a referral and a suggestion to try a different shampoo.
Take these five things with you
- Dated photographs of your parting and crown, taken monthly in the same light. This is the single most persuasive thing you can bring.
- A start date. "Since about March" is far more useful than "for a while", because the two to four month delay between trigger and shedding is how the cause gets identified.
- Your other symptoms, written down. Energy, temperature, weight, periods, skin, sleep, mood, bowels.
- Your medication and supplement list, including anything started or stopped in the last year.
- Family history. Whether your mother, father or siblings have the same pattern, and at what age it began.
It is also fine to say plainly that the hair loss is distressing you. That is relevant clinical information, not an imposition, and it changes how seriously a symptom gets weighted.
What does a normal result actually rule out?
A normal panel rules out the treatable systemic causes it tested for, and nothing more. It does not rule out androgenetic hair loss, which is diagnosed by examining the scalp and the pattern rather than by blood, and it does not rule out telogen effluvium, which has no diagnostic blood test at all and is identified from the history.
Two nuances are worth understanding before you read your own results.
The first is that laboratory reference ranges describe the spread of a population, not an ideal for every tissue. Ferritin is the standard example: a result can sit inside the normal range and still be low enough that dermatologists would want it raised before judging a hair problem, and thresholds above 30 or above 50 micrograms per litre are commonly cited in dermatology practice. Guidelines do not all agree on a number, so this is a conversation to have with your GP rather than a cutoff to insist on.
The second is that a borderline result usually needs repeating rather than acting on. Prolactin in particular rises with stress, exercise and even a difficult blood draw, so a single mildly raised value is normally rechecked before anything follows from it.
Which tests are not worth paying for?
Direct to consumer testing has grown fast, and a good deal of what is marketed for hair loss has no clinical value. These are the ones to avoid, because they produce official looking numbers that no NHS clinician will act on.
- Saliva hormone panels. Poorly correlated with blood levels for most hormones. Not used in endocrinology for this purpose.
- Hair mineral analysis. Results vary between laboratories on the same sample and are affected by shampoo, dye and water. Not a valid measure of nutritional status.
- IgG food intolerance tests. Not supported as a diagnostic tool by allergy bodies. They tend to produce long avoidance lists, and restrictive eating is itself a shedding trigger.
- Broad private hormone screens sold without symptoms. They generate borderline findings at a high rate, and the usual outcome is anxiety plus a repeat test on the NHS.
- Genetic hair loss risk kits. They mostly confirm what your family history already told you, and they do not change what treatment is available to you.
The exception is a straightforward private blood panel covering the same standard markers as above, taken through a properly accredited laboratory, if you cannot get them done otherwise. Those are real tests. It is the unvalidated methods that are the problem, not private testing as such.
What happens after the results come back?
Most findings lead somewhere specific. This is roughly how each one is usually handled, so you know what to expect and what to ask about next.
| Finding | Typical next step | When hair usually responds |
|---|---|---|
| Underactive thyroid | Thyroid hormone replacement, then repeat bloods to get the dose right | 6 to 12 months after levels are stable, not immediately |
| Low ferritin or anaemia | Iron supplementation and a look for the cause, especially heavy periods or gut symptoms | 3 to 6 months, and stores take longer to refill than blood counts |
| Low vitamin D or B12 | Supplementation at a dose your GP sets, with a recheck | Variable, and often only part of the picture |
| Raised androgens, likely PCOS | Further assessment, possibly ultrasound, and a discussion of hormonal or anti androgen options | Slow. Hair changes lag other improvements considerably |
| Raised prolactin | Repeat test, medication review, and imaging if it stays high | Once the cause is treated |
| Everything normal, diffuse shedding | Usually telogen effluvium. Identify the trigger, treat gently, review in a few months | Typically 3 to 6 months of shedding, then regrowth |
| Everything normal, patterned thinning | Androgenetic hair loss. Ask about minoxidil, and about referral if it is progressing quickly | Treatment is about slowing progression, so earlier is better |
If the answer turns out to be a shedding episode rather than a hormonal condition, our guide to sudden hair loss in women and what to do about it covers the recovery period. If it is thyroid, thyroid hair loss and whether it reverses explains the timeline in more detail.
What can you do while you wait for results?
Results take days to weeks, and treatment takes months to show at the surface. The useful thing to do meanwhile is protect the hair you already have, because breakage stacked on top of shedding is what makes hair look suddenly much thinner. Gentle handling, no tight styling, no brushing soaking wet hair, and heat protection every time.
On supplements, wait for the numbers. Correcting a deficiency the test finds is worth doing. Loading up on iron or high dose biotin before the blood is taken can both distort the results and, in the case of iron, do harm. Our honest look at which vitamins actually help hair growth separates the ones with evidence from the ones with marketing.
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When should you ask for an urgent appointment?
Most hair loss can wait for a routine appointment. Some presentations should not, either because the hair loss can become permanent or because it is signalling something that needs attention now.
Ask for an urgent appointment if you have
- Hair loss with scalp pain, burning, scaling, pustules or scarring
- Rapidly expanding bald patches, or loss of eyebrows, eyelashes or body hair
- Hair loss alongside palpitations, tremor, marked weight loss or heat intolerance
- Headaches with vision changes, or milky nipple discharge
- Clumps of hair coming out within weeks of starting a new medication
- Severe fatigue and breathlessness with the shedding
- Any noticeable hair loss in a child
Scarring conditions are the reason the first line matters. Where scalp inflammation is destroying follicles, the hair does not come back, so treatment is about stopping the process early rather than restoring what is gone.
Frequently asked questions
Can I ask my GP for a ferritin test specifically?
Yes, and it is a reasonable request with unexplained shedding, particularly if you have heavy periods, a vegetarian or vegan diet, or a history of low iron. Ferritin is not always included by default in a basic blood panel, so naming it makes a genuine difference to whether it gets done.
Do I need to fast before hormone tests for hair loss?
Not for thyroid, ferritin, vitamin D, B12 or prolactin. Fasting is sometimes requested for glucose or HbA1c and for a lipid panel, which may be included if PCOS is being assessed. Ask the clinic when you book rather than assuming either way.
Should I stop taking biotin before a blood test?
Tell the clinic what you take and follow their advice. High dose biotin interferes with several laboratory immunoassays, including thyroid and cardiac tests, and can produce misleading results. Clinics commonly ask people to stop it for a couple of days beforehand, but the interval depends on the dose and the laboratory.
How long do hormone test results take?
Routine blood results usually reach the practice within a few days to a couple of weeks, depending on the test and the local laboratory. Ask how you will be told, and follow up if you hear nothing, since no news is not a reliable signal that everything was normal.
Can I get these tests privately if my GP declines?
Yes. A standard panel through an accredited private laboratory covering thyroid function, full blood count, ferritin, vitamin D and B12 is a legitimate option and the results are meaningful. Avoid saliva hormone panels and hair mineral analysis, whatever the marketing claims, because no clinician will act on them.
Why did my GP examine my scalp instead of testing my blood?
Because the most common cause of long term thinning, androgenetic hair loss, is diagnosed by looking at the pattern of loss and the calibre of the hairs rather than by blood. A scalp examination and a pull test give information that no blood panel provides, so it is a sign of a thorough assessment.
Is there a test that shows why hair is thinning?
There is no single test. Diagnosis comes from combining the pattern of loss, the timeline, your other symptoms and a targeted blood panel. That is why the history you bring matters as much as the tests, and why a start date and monthly photographs are so useful.
Should I see a trichologist or a GP first?
See a GP first, because only a doctor can order blood tests, review your medications, prescribe treatment and refer you to a dermatologist. Trichology is unregulated in the UK and standards vary widely. A good trichologist can be helpful afterwards, but not instead.
Where to go from here
Write down your start date, take a photograph of your parting today, list your medications and supplements, then book the appointment and ask for the baseline panel by name. If the tests find something, most of it is treatable. If they come back clear, that narrows things usefully rather than being a dead end.
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Last updated: August 2026. This article is general information about the tests commonly used to investigate hair loss in the UK. It is not medical advice, and it does not replace an assessment by a GP, pharmacist or dermatologist.
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