Topical minoxidil, a non-prescription drug applied to the scalp as a liquid or foam, regrows and thickens hair in hereditary pattern hair loss in men and women. Evidence is strong, though regrowth is usually partial and lasts only with ongoing daily use. Main risks are local and reversible: scalp itching and rash, unwanted facial or body hair, and a temporary early shed. Household cats face real danger from contact. (Full Review)

Protocol

Topical regimen, men

5% solution or foam, twice daily

1 mL solution or half a capful of foam per application, applied to the thinning scalp

Topical regimen, women

5% foam, once daily

Half a capful; alternative 2% solution, 1 mL twice daily

Time of day

Morning and evening for twice-daily use

Dry scalp; at least 4 hours before washing; evening application finished 2 or more hours before bed

Time to effect

Peak results

~12 months

Success: stable or reduced shedding by 6 months, visible density gain by 12 months

Visible regrowth

4–6 months

Assessing at 4–6 months prevents abandoning treatment before benefit appears

Shedding slows

2–3 months

Temporary shedding in weeks 2–8 usually settles

Benefits

High: Scalp hair regrowth in pattern hair loss

Medium: Eyebrow and beard enhancement

Low: Faster regrowth in other non-scarring hair loss; better hair-related quality of life

Speculative: Preventing pattern hair loss before visible thinning

Contraindications

Pregnant or breastfeeding women, and women actively trying to conceive

People under 18 years (not studied)

People with patch-test-confirmed allergy to minoxidil

People with an inflamed, sunburned, or broken scalp (e.g., active scalp psoriasis, open wounds)

People with sudden, patchy, or unexplained hair loss, or loss without family history, until diagnosed

People with heart disease unless medically supervised (symptomatic coronary artery disease, heart failure of New York Heart Association Class III–IV, heart attack within the past 90 days, uncontrolled arrhythmia)

Households with cats that cannot be kept away from treated skin and bedding

Key Interactions

Antihypertensive drugs (amlodipine, lisinopril, losartan, guanethidine)

PDE5 inhibitors and nitrates (sildenafil, tadalafil; nitroglycerin, isosorbide mononitrate)

Absorption-enhancing topicals (tretinoin, betamethasone, anthralin)

Over-the-counter aspirin and salicylates (aspirin 75–81 mg)

Over-the-counter hair chemicals (hair dyes, relaxers, permanent waves)

Blood-pressure-lowering supplements (hibiscus, garlic extract, beetroot nitrate, L-citrulline)

Microneedling

Oral minoxidil

Risk & Side Effects

High: Scalp irritation and contact dermatitis; unwanted facial and body hair

Medium: Toxicity in household cats and dogs

Low: Systemic vasodilator effects; temporary shedding at treatment start; possible fetal harm in pregnancy; severe toxicity after accidental ingestion

Speculative: Accelerated hair loss after stopping

Monitoring

Marker	Target	Why
Scalp hair density (magnified count)	No established target; track change from own baseline	Objective response
Ferritin	70–150 ng/mL	Iron stores for hair growth
TSH	0.5–2.5 mIU/L	Thyroid-driven shedding
25-hydroxyvitamin D	40–60 ng/mL	Deficiency linked to hair loss
Blood pressure	Below 120/80 mmHg	Detect vasodilator effect
Resting heart rate	50–70 beats/min	Detect reflex rise
Free testosterone (women with androgen signs)	Lower half of the laboratory reference range	Identify hormone excess

Cadence: Photographs at 3, 6, and 12 months, then every 12 months; blood pressure and heart rate at 2–4 weeks, then every 6–12 months, or sooner with symptoms; blood tests every 12 months only if earlier results were abnormal

Qualitative Assessment

Shedding volume (brush, shower drain, pillow)
Part width and crown coverage in photos
Hair thickness and styling ease
Scalp comfort (itch, flaking)
New facial or body hair
Ankle swelling, palpitations, or dizziness

Topical Minoxidil for Hair Regrowth

Protocol

Benefits

Risk & Side Effects

Monitoring

Qualitative Assessment