Hair loss: causes, tests and when to see a doctor
Gradual thinning, diffuse shedding and bald patches can have different causes. Examining the scalp helps establish which tests are useful and which treatment makes sense.
Hair loss has more than one cause, and the same set of tests is not appropriate for everyone. Gradual thinning may be hereditary; diffuse shedding may follow illness, childbirth or deficiencies, while bald patches may indicate another condition. The doctor starts with the history and a scalp examination. Pain, inflammation or rapid hair loss warrant a more prompt assessment.
The first clue
Gradual thinning, diffuse shedding or bald patches?
The first clue is the pattern: is the hair gradually thinning, shedding across the scalp or disappearing in clearly defined patches?
- Progressive thinning: the hairline may recede, the crown may thin or the parting may widen. Androgenetic alopecia affects both men and women.
- Diffuse shedding: more hairs are lost from several areas, without a single patch. One possible explanation is telogen effluvium.
- Bald patches: these can occur in alopecia areata and in other conditions; their appearance needs assessment.
The doctor also looks for redness, scaling, broken hairs or skin changes. The same words, ‘my hair is falling out’, can describe different problems. A photograph helps track progress but does not always show every sign on the scalp.
Sources: Spitalul Clinic Colentina, alopecia protocol, p. 1, for clinical patterns; Wolff and colleagues, The Diagnosis and Treatment of Hair and Scalp Diseases (2016).
History matters
What can happen before hair loss begins
Diffuse shedding may begin a few months after an illness, childbirth or another event affecting the body.
This is why the history includes the period before the hair loss. Mention surgery, weight loss, dietary restrictions and changes in medicines. Iron deficiency and thyroid disorders are possible causes in certain situations, but cannot be identified simply by the number of hairs in your brush.
Hairstyles that repeatedly pull on the roots can cause traction alopecia. Some medicines may contribute to shedding, but do not stop prescribed treatment without discussing it with your doctor. Several causes can coexist, including hereditary thinning alongside temporary shedding.
Telogen effluvium may improve once the cause is addressed, but progress is assessed over time. A promise of guaranteed regrowth before a diagnosis ignores the difference between temporary forms and those that permanently damage the follicle.
Sources: Wolff and colleagues (2016); American Academy of Dermatology, causes of hair loss.
Investigations with a purpose
Which tests for hair loss are useful?
Tests should investigate a specific suspicion. There is no universal test package that explains every case of hair loss.
For hereditary thinning with a typical appearance, the history and examination may be sufficient. For unexplained diffuse shedding, the doctor may check iron stores or thyroid function. In women, irregular periods, acne or unusual facial hair growth may point towards hormonal investigations.
If the scalp is inflamed or a scarring condition is suspected, the dermatologist may recommend examination with a dermatoscope, other tests or a biopsy. These investigations are selected after the consultation, not beforehand simply because they are included in a laboratory package.
Do not start iron, zinc or biotin without a medical reason. Supplements do not replace a diagnosis, and taking them without a deficiency may be unnecessary or harmful. Bring the packaging or a list of products and doses used.
Sources: Wolff and colleagues (2016), clinical assessment and tests; ANMDMR, authorised Thyrofix patient leaflet, revised June 2026, pp. 3–4, biotin warning; AAD, diagnosis and supplements.
Timely assessment
When to arrange an appointment without delay
Arrange an earlier consultation if hair loss progresses rapidly or occurs with pain, redness or scalp inflammation.
Some inflammatory forms of alopecia can destroy follicles and leave areas where hair no longer grows. Bald patches, loss of eyebrows or eyelashes and significant scaling also deserve assessment. You do not need to wait for things to worsen if the change worries you or affects your wellbeing.
A hair loss consultation can begin with a description of symptoms and photographs. The doctor decides whether an in-person examination by a dermatologist is needed. Samples and biopsies are taken in a healthcare setting, not by video.
Sources: Wolff and colleagues (2016), scarring alopecias; AAD, signs and causes of hair loss.
A clear history
What you can do before the assessment
Before the assessment, treat your hair gently and prepare a brief history of the changes you have noticed.
Avoid very tight hairstyles and treatments that damage the hair shaft. To compare changes, take photographs in the same light and from the same angle. Repeatedly checking the hairs in your brush cannot establish the cause.
- Note when the change began and which areas are affected.
- Prepare a list of medicines, supplements and treatments already tried.
- Mention family history, recent illnesses, pregnancy or breastfeeding and dietary changes.
- Explain what bothers you most and what you expect from treatment.
After diagnosis, ask what the treatment aims to achieve: reducing shedding, controlling inflammation or stimulating growth. Results are often assessed after months, and goals differ depending on the cause. Agree when the plan should be reviewed and which changes warrant an earlier consultation.
Guidance
Discuss the changes you have noticed with a doctor
The history and scalp examination guide investigations. The doctor decides whether assessment needs to continue in person.
Prepare a description of how things have changed
Bring photographs, your treatment list and questions. Investigations and treatment goals are agreed after assessment.
Background reading
Medical sources
Sources checked on 27 September 2026. Medical review of the draft is pending.
The Colentina protocol is an older document with no visible revision date; it is cited only for descriptions of patterns, not current treatment regimens. Assessment and supplements are discussed with support from the international sources listed. The ANMDMR leaflet is cited solely for test safety, not as a treatment for hair loss.
Questions
Frequently asked questions about hair loss
Does hair loss mean I am low in iron?
The cause cannot be established from the appearance of the hair loss alone. Iron deficiency is one possible explanation; the history and examination indicate whether tests would be useful.
Can I use the same treatment as someone else in my family?
The diagnosis and contraindications may differ. Speak to your doctor before starting medicines, especially during pregnancy, while breastfeeding or if you are planning a pregnancy.
