Hair loss: practical guide to causes, tests, and treatments

Hair loss feels personal, but you don’t have to guess what’s happening. This page gives clear steps: quick checks you can do, the tests that matter, and treatments that actually help most people. Skip the myths and get straight to what to try now.

What usually causes thinning

The most common culprit is androgenetic alopecia — genetic sensitivity to DHT that causes a receding hairline in men and diffuse thinning across the crown in women. Hormone changes (thyroid problems, postpartum shifts, or polycystic ovary syndrome) are also common triggers. Sudden, heavy shedding usually points to telogen effluvium, which often follows illness, surgery, a major stress, or starting a new medication. Some prescriptions — certain blood pressure drugs, strong retinoids, chemotherapy, and a few mood or thyroid medicines — can cause hair to thin. Nutritional gaps like low iron or vitamin D, plus restrictive diets, frequently make shedding worse.

Quick tests and what to ask your doctor

If hair loss is sudden, patchy, or paired with scalp pain or redness, see a clinician right away. For slower thinning, start with simple, useful tests: complete blood count, TSH (thyroid), ferritin (iron stores), and vitamin D. Women with irregular cycles should consider an androgen screen for PCOS. A primary care provider or dermatologist can do a pull test and use trichoscopy (a close scalp exam) to spot patterns. If labs are normal but hair keeps falling after three to six months, ask about a scalp biopsy — it can show scarring alopecia or other causes that change treatment choices.

Two treatments have the best evidence for pattern hair loss. Topical minoxidil is available over the counter and helps many people keep and sometimes regrow hair when used consistently for months. Oral finasteride reduces DHT and slows or reverses thinning in men; discuss possible sexual side effects and long-term use with your clinician. Other options include platelet-rich plasma (PRP), low-level laser therapy, and off-label prescriptions for select patients — results vary and depend on the provider’s skill.

Daily habits matter. Use a gentle shampoo, avoid tight hairstyles and frequent heat or harsh chemical treatments, and choose soft, breathable hats or wigs. Eat a balanced diet with adequate protein, iron, zinc, and basic B vitamins; supplements can help if tests show a deficiency but won’t undo genetic loss. Track progress with photos every month — changes are slow, and photos show real trends better than memory.

When to see a specialist: if tests don’t find a cause, shedding continues despite fixes, or you’re considering procedures like transplants, talk to a dermatologist who focuses on hair. A skilled clinician will offer realistic options, monitor side effects, and create a stepwise plan. Want deeper reading? Browse our site for articles on lab checks, medication side effects, and affordable treatment choices available in Canada.