Hair loss diagnosis: trichoscopy, tests and biopsy (and what to expect)

Blood tests: when and which

Not every type of hair loss needs blood tests, but some do. The aim is to find treatable causes that trigger or worsen shedding.

One well-known review suggests a full blood count, ferritin, thyroid function (TSH) and vitamin D for everyone with hair loss ^[6]. Current practice is more selective and guided by your history:

• Ferritin and a full blood count, especially in women with diffuse shedding. In a series of 2,851 women with telogen effluvium, ferritin was low in 46.5% of those tested ^[7].
• Thyroid function, if there are symptoms or the shedding is diffuse without a clear cause.
• Other tests, such as hormone levels in women with irregular periods, acne or excess body hair, as your doctor advises.

Blood tests have limits too. In another series of 131 patients with non-scarring hair loss, only 15.3% had an abnormal result, and correcting it with supplements did not improve hair density ^[8]. So tests are ordered with judgement rather than by routine, and supplements are not a substitute for treatment.

If you are used to results from the NHS or another European system, note that laboratories in Spain usually report ferritin in ng/mL, which is numerically the same as µg/L. Your doctor will interpret the figures for you either way.

When a scalp biopsy is needed

A biopsy is reserved for cases where the diagnosis is uncertain ^[9]. It is essential when scarring alopecia is suspected ^[6], because it confirms the type and guides treatment that should start as early as possible.

What it involves, in outline:

1. The site is chosen. In non-scarring hair loss, the most affected area; in scarring alopecia, the active edge, found with the dermatoscope ^[9].
2. Local anaesthetic is given.
3. A small cylinder of skin is removed with a circular punch, usually 4 mm across ^[9].
4. The wound is closed, often with a single stitch, and covered.
5. The sample goes to the pathology laboratory.

In the laboratory, horizontal sections at several levels allow the follicles to be counted and classified ^[9]. The clinical information sent with the sample can be decisive for the diagnosis ^[9].

There is follow-up afterwards: a visit to remove the stitch, if there is one, and another to go through the report and decide on treatment. The scar is small and usually hidden by hair.

Other causes worth recognising

• Telogen effluvium. Diffuse shedding that starts about 3 to 4 months after a trigger, such as childbirth, a high fever or a crash diet. The cause is found through history and blood tests ^[10].
• Alopecia areata. An inflammatory, non-scarring condition, ranging from small round patches to complete loss of body hair ^[11]. It usually needs a dermatologist.
• Frontal fibrosing alopecia. A scarring alopecia that pushes the frontal hairline back and can affect the eyebrows. In a Spanish series of 355 patients, most were women, with an average age of 61 ^[12]. It needs diagnosis and treatment by a dermatologist.

How to prepare for your consultation

Arriving with your information in order saves time and improves the diagnosis:

• Older photos that show your hair a few years ago, if you have them.
• Recent blood tests and previous reports, including any from your home country.
• A list of the medicines and supplements you take, with start dates.
• What you have already tried for hair loss, for how long and with what result.
• Any major change in the preceding months: childbirth, an operation, a diet or a period of severe stress.

What can be done online, and what cannot

With guided photographs, a video consultation and a local blood test, most cases of pattern hair loss and telogen effluvium can be assessed. That is how we work with patients across Spain, in English or Spanish.

Some cases cannot be managed online: suspected scarring alopecia, extensive alopecia areata, marked inflammation or a picture that does not fit. In those cases we tell you plainly and explain which examination you need. If a biopsy is required, we guide you to have it done with a dermatologist.

How it works with us in Spain

We start with a medical video consultation. We guide you through taking the scalp photographs and go through your full history. If your case calls for it, we request blood tests at a laboratory near you.

Your doctor brings everything together and explains the likely cause and the plan. Rejuvelook's AI organises your information for the doctor; it guides, but it does not diagnose. If the diagnosis is pattern hair loss, the next step is usually medical treatment for hair loss, with an electronic prescription when appropriate. We can give you a written summary in English for your GP or dermatologist at home.