Demographic branching
The calculator's first decision is not "what dose"; it is "are you a candidate for systemic 5-alpha-reductase inhibition at all." That gate runs on three inputs: biological sex, menopausal status (for women), and a Norwood (male) or Ludwig (female) stage that confirms the pattern is androgenetic alopecia rather than something cicatricial, autoimmune, or telogen.
Three branches drop out of that gate.
Male AGA. Standard branch is finasteride 1 mg/day PO plus minoxidil; topical 5% twice daily by default, with low-dose oral minoxidil (LDOM, titrated 1.25 → 5 mg evening) as an alternate route. A cautious sub-branch drops finasteride to 0.5 mg/day for users who want to titrate side-effect exposure; that variant has no RCT validation and rests on a pharmacokinetic argument that scalp DHT suppression outlasts plasma half-life.
Premenopausal women. Finasteride is contraindicated unless reliable contraception and an endocrine workup are in place, because finasteride is FDA pregnancy Category X; handling crushed tablets is enough to feminize a male fetus. The calculator therefore returns minoxidil-only (topical 2% solution first-line, 5% foam QD as off-label option, or LDOM titrated 0.625 → 2.5 mg) and surfaces an explicit clinician-consult notice for the finasteride decision.
Postmenopausal women. The systemic branch reopens. Finasteride at 2.5–5 mg/day PO is first-line per the 2026 JAAD review on frontal fibrosing alopecia and adjacent female-pattern indications (PMID 39800209); spironolactone is the historical alternative, not a calculator output here. Minoxidil sits on top at the female dose ceiling.
Why those specific drugs and doses
Finasteride 1 mg/day is the FDA-labeled dose for male AGA (Propecia). The dose was chosen from the original Merck Phase 3 program because it produced near-maximal scalp DHT suppression with no further benefit at 5 mg; that ceiling is why the calculator does not offer a higher daily dose for men. The 5 mg/day Proscar dose is for benign prostatic hyperplasia, not hair, and the cautious-mode 0.5 mg variant exists in dermatology practice without an RCT; the calculator labels it as such.
Topical minoxidil 5% twice daily is the FDA-labeled male regimen; 2% is the female default. The 2025 meta-analysis of four RCTs (N=279, PMID 39425514) found oral and topical minoxidil produced statistically equivalent hair density and diameter changes in AGA; which is why the calculator offers either route rather than ranking them. Hypertrichosis was twice as common with oral.
Sublingual / oral low-dose minoxidil dose-finding comes from Sinclair's 2025 RCT (PMID 39774750): 1.35 mg and 4.05 mg increased mean fibre diameter; 0.45 mg did not. That dose-response anchors the calculator's male LDOM target window (2.5–5 mg).
Assumptions and limits
The calculator assumes the diagnosis is androgenetic alopecia in a male AGA pattern (Norwood) or female AGA pattern (Ludwig). It does not handle alopecia areata, traction alopecia, frontal fibrosing alopecia, telogen effluvium, lichen planopilaris, or any scarring alopecia; those need a dermatologist, often a biopsy, and a different drug class (intralesional steroids, hydroxychloroquine, JAK inhibitors). Misclassifying a scarring alopecia as AGA wastes 12 months on the wrong protocol while permanent follicle destruction continues.
The calculator assumes the user is not pregnant and not planning pregnancy in the adherence horizon. Finasteride is pregnancy Category X. The premenopausal-female branch enforces this by withholding the finasteride output entirely.
The adherence horizon is 6–12 months minimum for visible response, with peak effect at 12–18 months. The shedding timeline encodes the 2–8 week dread shed (synchronized telogen exit, often a response indicator, not a treatment failure), the 16–24 week density inflection, and the 52–78 week plateau.
What the calculator does not model: the post-finasteride syndrome (PFS) controversy is acknowledged in warnings but not quantified; there is no consensus incidence number to encode. Dutasteride is mentioned in the FFA review (PMID 39800209) but is not an output; it is a stronger 5-AR inhibitor used off-label and belongs in a clinician conversation, not a calculator default.
Unit conventions
Finasteride is reported in mg/day PO. The 1 mg male dose, the 0.5 mg cautious variant, and the 2.5–5 mg postmenopausal female range are all whole-tablet or half-tablet doses against the commercially available 1 mg and 5 mg strengths.
Topical minoxidil is reported as percent concentration plus mL/dose plus doses/day. The 5% foam at 1 mL twice daily delivers ~100 mg/day of drug to the scalp, of which a small fraction is absorbed systemically; that fraction is why oral and topical routes can produce comparable hair outcomes despite a 50× difference in nominal dose.
Oral minoxidil (LDOM) is reported in mg/day PO. The titration ladder is start → target-min → target-max with a hard ceiling: 5 mg/day for men, 2.5 mg/day for women (lower because hypertrichosis tolerance is lower in women).
Why this is documentary, not prescriptive
Finasteride and oral minoxidil are prescription-only drugs in Romania, the EU, the UK, and most other jurisdictions. Topical minoxidil is OTC in the US and prescription-only in some EU markets. This calculator is information-only. It shows what the published RCT and meta-analysis evidence converges on for each demographic branch, with sources visible inline and warnings (pregnancy Category X, EMA/MHRA suicidal-ideation labeling update, persistent sexual dysfunction) surfaced alongside the dose.
Obtain a prescription through a dermatologist or qualified telemedicine service. Get baseline photos under consistent lighting, optional baseline labs (total T, SHBG, DHT, TSH, ferritin, 25-OH-D) to rule out non-androgenic causes, and log mood weekly during weeks 1–12. Stop and reassess if any sexual, cognitive, or mood change persists more than two weeks. Every PMID on this page was verified live against PubMed by the same INT-01 citation guardrail that gates the calculators on this site.