What Your Hair Is Telling You About Your Health

Hair grows out of follicles fed by some of the smallest blood vessels in the body, and it’s metabolically expensive to grow. Your body deprioritizes hair when other systems are stressed, which is why hair health tracks so closely with iron, thyroid, protein, sleep and stress. The signs are useful precisely because the body is honest with you here.

Why hair health reflects your overall wellbeing

Each hair follicle cycles through growth (anagen, 2–6 years), transition (catagen, 2–3 weeks) and shedding (telogen, 3 months). About 90% of your scalp is in anagen at any given time.

When something stresses the body — major illness, postpartum, severe stress, crash diet, surgery — a chunk of follicles drop into telogen at once. Three months later you shed. The shed is the last symptom, not the first.

8 things your hair may be telling you

1. Excessive shedding (>150/day): often telogen effluvium — a stress event 3 months ago is the usual culprit. Iron deficiency, thyroid changes, postpartum and rapid weight loss are the common triggers.

2. Dry, brittle hair: low thyroid output (hypothyroidism), dehydration or low protein. Worth checking TSH if persistent.

3. Oily scalp + acne flare: often hormonal — cycle changes, PCOS, or stress-driven cortisol shifts.

4. Slow growth or thinning: iron and ferritin matter most. Ferritin under 30 ng/mL is associated with shedding even when hemoglobin is normal.

5. Premature greying: mostly genetic, but B12 deficiency and chronic stress can accelerate it. Premature here means before 25 in white populations, before 30 in Asian, before 35 in Black populations.

6. Patchy hair loss: alopecia areata is autoimmune; see a dermatologist. Round, smooth bald patches the size of a coin are the classic pattern.

7. Receding hairline / temporal thinning (men or women): androgenetic — the most common pattern. Treatable but progressive without intervention.

8. Itchy, flaking scalp: seborrheic dermatitis, fungal infection, or product buildup. If it doesn’t resolve with a medicated shampoo (ketoconazole, zinc pyrithione) in 2 weeks, see a doctor.

Nutrients that support hair health (Canadian sources)

Iron and ferritin: beef, dark leafy greens, lentils, fortified cereals. Vitamin C with iron-rich meals doubles absorption.

Protein: 0.8–1.2g per kg body weight per day. Hair is mostly keratin, a protein.

B12 and folate: meat, eggs, dairy, leafy greens. Vegans should supplement B12.

Zinc: oysters, beef, pumpkin seeds. Deficiency causes shedding.

Biotin: contrary to marketing, supplemental biotin only helps people with actual biotin deficiency, which is rare in Canada. Save your money.

When to talk to a doctor about hair loss in Canada

See your family doctor if shedding has lasted more than 3 months, if there’s patchy loss, or if it’s accompanied by fatigue, cold sensitivity or weight changes (possible thyroid).

A standard workup includes CBC, ferritin, TSH, vitamin D and B12. In Ontario, BC, Alberta, Quebec and most provinces these are covered. Testosterone and DHEA-S if PCOS is suspected.

For dermatologist referral: family doctor first. Wait times in Ontario are 3–9 months. In Quebec, 1–6 months via FMG. Telehealth dermatology services (Maple, Felix) bypass the wait but are paid out of pocket.

The bottom line

Hair is a slow, honest readout of how the body is doing. If shedding starts, look back three months and ask: was there illness, surgery, severe stress, weight loss, or a baby? Get bloodwork (CBC, ferritin, TSH, vit D, B12) before assuming a topical product will fix it.

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