BalanzGM is reader-supported. Some links on this page are affiliate links — if you buy through them we may earn a commission at no extra cost to you. It never changes what the evidence section says. See our affiliate disclosure.
This article summarizes published evidence — the original classification papers, a peer-reviewed review of them, FDA drug labeling and manufacturer clearance information, each cited below. It is written by journalists, not clinicians, and has not been reviewed by a physician. Talk to a doctor or a board-certified dermatologist before starting or stopping any treatment. Full medical disclaimer.
What the status labels on this page mean
- FDA-approved
- The FDA reviewed the evidence and approved this drug for pattern hair loss.
- FDA-cleared
- Allowed on the market through the 510(k) route because it is judged similar to a device already sold — not the same as the FDA independently approving its effectiveness.
What this page found
- There are two scales in common use: Hamilton–Norwood for men (seven types plus an A variant) and Ludwig for women (three grades).[1, 2, 3]
- Norwood Type III is the threshold the original classification treats as the minimum for baldness — everything before it is recession, not loss.[1]
- The Ludwig scale describes something different from the male pattern: diffuse thinning on the crown with the frontal hairline preserved.[3]
- Nobody publishes a stage at which treatment stops working. The most honest marker we found is a manufacturer’s own limit: HairMax restricts the indication for its cleared devices to Norwood IIa–V and Ludwig I–II.[5]
- Self-assessing from photographs is rough, and the scales were designed for clinicians describing populations, not for you diagnosing yourself in a bathroom mirror.
Why these scales exist at all
Pattern hair loss progresses in a recognisable order, which is unusual and useful. Hamilton described the types in 1951 and Norwood revised the classification in 1975; Ludwig published the female scale in 1977.[1, 2, 3] They were built so that clinicians and researchers could describe the same thing in the same words — not to give you a score.
That origin explains their two practical uses today. A trial or a device clearance can state which stages it covers, and you can track your own change over years against a fixed description instead of arguing with an old photograph.
The Norwood scale, stage by stage
Hamilton–Norwood stages
| Stage | What defines it |
|---|---|
| Type I | Minimal or no recession of the hairline. |
| Type II | Symmetrical triangular recession at the front and temples. The hairline does not recede more than about 3 cm in front of the external ear canal, with slight thinning in the mid-frontal area. |
| Type III | The minimum stage considered baldness. Deep symmetrical recession at the temples, with those areas bare or only sparsely covered. |
| Type III vertex | A variant where loss is chiefly at the crown, with limited frontotemporal recession. |
| Type IV | More severe frontotemporal recession than Type III, plus sparse hair or none at the crown — the two areas still separated by a band of moderately dense hair across the top. |
| Type V | Crown and frontotemporal areas remain separate but the boundary is less distinct; the connecting band narrows and thins noticeably. |
| Type VI | The connecting bridge of hair is gone. Frontotemporal and crown areas join into one enlarged bald region. |
| Type VII | The most severe. Only a narrow horseshoe band of hair remains at the sides and back. |
The Type A variant, which is easy to miss
Alongside the numbered types there is a Type A series — IIA, IIIA, IVA, VA. It describes a different route to the same place: the front hairline recedes back continuously, with no island of hair left in the mid-frontal area and no separate crown balding developing at the same time.[1]
It matters because someone progressing through the A series can look like an earlier standard stage while actually losing ground steadily from the front. If your hairline is moving back as a single line rather than forming the usual M shape, this is the pattern being described.
The Ludwig scale for women
Ludwig’s 1977 classification has three grades, and its defining feature is what it preserves rather than what it loses: the frontal hairline stays.
Ludwig grades
| Grade | Ludwig’s description |
|---|---|
| Grade I | Perceptible thinning of hair on the crown, limited in front by a line situated 1 to 3 cm behind the frontal hairline. |
| Grade II | Pronounced rarefaction of hair on the crown within the area seen in Grade I. |
| Grade III | Full baldness — total denudation — within the area seen in Grades I and II. |
The difference from the male pattern is not cosmetic. Because the loss is diffuse across the crown rather than a receding line, it is often noticed as a widening part or a thinner ponytail long before anything looks like a bald patch. The approved treatment picture for women is also different, and we cover it separately in our guide to female pattern hair loss.
The Savin scale, and why you may see it instead
Savin published a further female scale in 1992 using nine computer-generated images: eight stages of increasing crown thinning plus a separate category for detecting frontal anterior recession.[1, 4] It exists because not every woman’s loss keeps the frontal hairline, which the Ludwig scale assumes.
We were not able to obtain the anatomical description of each individual Savin stage from a primary source, so we are describing the scale’s structure rather than listing its stages. Where you see a clearance or a trial referring to Ludwig (Savin) grades, it is treating the two as equivalent for the crown.
Where treatment still applies — according to the people selling it
This is the question everyone actually arrives with, and the published literature does not answer it with a number. What does exist is more useful than an opinion: the range in which a manufacturer is willing to state its own product is indicated.
A manufacturer drawing its own boundary
HairMax’s FDA clearance information limits the indication for its devices FDA-cleared to men with Norwood-Hamilton classifications IIa to V and women with Ludwig (Savin) I-4 to II-1 or frontal patterns, and to Fitzpatrick skin types I to IV.[5]
Read that as a company telling you where it stops claiming its product works. It is a more candid answer than most editorial guidance on this question, and it is the only stage-specific boundary we found in a primary source.
HairMax product and clearance information, checked 8 September 2026.
For the drugs, the boundary is implicit rather than stated. The pivotal finasteride trial enrolled men aged 18 to 41 with mild to moderate vertex hair loss[6, 7], so its results describe that group. The FDA-approved minoxidil label describes its effect on the crown area and warns that results may take three to six months[8]. Neither label states a stage past which the drug will not help — and neither claims to regrow hair where the follicle is gone.
The practical version. The scales run from I to VII, but the useful distinction is much simpler: are there still miniaturised hairs in the area, or is the scalp smooth? Treatments act on follicles that are still cycling. Nobody can tell which of those you have from a photograph, which is why this is a question for someone examining your scalp.
Getting an actual assessment rather than a guess
Working out your stage from photographs is rough, and the more important question — whether what you have is pattern hair loss at all — cannot be answered that way. Sesame Care is a US marketplace listing upfront cash prices for consultations, including hair loss visits, so you can see the cost before booking.
Sesame Care is a US telehealth marketplace that lists upfront cash prices for appointments. The link below is an affiliate link: if you book, we may earn a commission at no extra cost to you.
See hair loss consultation prices →Using the scale on yourself, honestly
- Photograph consistently, not frequently. Same light, same angle, same dry hairstyle, every three months. Comparing two shots taken in different bathrooms is how people convince themselves of change in either direction.
- Judge the crown from above. The Ludwig and Norwood crown descriptions are about an area you cannot see in a mirror.
- Do not expect to move backwards through stages. The trials measured hair count in a marked area, not stage reversal. Treating early is about how much you keep, not how far you rewind.
- Sudden or patchy loss is a different question entirely. These scales describe a gradual, symmetrical, patterned process. Shedding that came on quickly, in patches, or with scalp symptoms is not what they describe, and it is worth having looked at rather than classified.
What each band of the scale usually means in practice
The scales describe. They do not prescribe. But they do map onto what is actually on offer, because the manufacturers themselves write their indications in these terms — and knowing which band you are in tells you which conversation is worth having.
| Where you are | What the published indications and labels cover |
|---|---|
| Norwood I–II, or Ludwig I | This is the band where the approved drugs have the most to hold on to. Topical minoxidil FDA-approved is available over the counter; oral finasteride FDA-approved is prescription-only and approved for men.[6][8] Nothing here is urgent, and nothing here is a reason to buy a device first. |
| Norwood IIa–V, or Ludwig I–II | The band HairMax limits its own FDA clearance to FDA-cleared.[5] It is also the band the drug trials largely recruited from — the 1,553-man finasteride trial studied men with mild to moderate vertex loss.[7] |
| Norwood VI–VII, or Ludwig III | Beyond the range the device clearance covers, and beyond what the drug trials measured. Published evidence thins out sharply here, and this is a dermatologist or surgical conversation rather than a treatment you select from a website. We are not going to give you an expected result, because the trials do not have one. |
| Sudden, patchy, or with scalp symptoms | Not this scale at all. See a clinician rather than picking a stage. |
Where the drugs sit, what they cost and what they do is covered in how finasteride and minoxidil work and what treatment actually costs per year.
Where to go next
Frequently asked questions
What Norwood stage am I?
Type III is the point the original classification treats as the minimum for baldness: deep symmetrical recession at the temples, with those areas either bare or only sparsely covered. Type III vertex is the variant where the loss is mainly at the crown. Below that, Type II is a symmetrical triangular recession at the front that does not extend more than about 3 cm in front of the ear canal. Self-assessment from photographs is rough; a clinician looking at your scalp is the reliable version.
What is the Ludwig scale?
It is the three-grade scale for female pattern hair loss, published by Erich Ludwig in 1977. Grade I is perceptible thinning on the crown, bounded at the front by a line 1 to 3 cm behind the frontal hairline. Grade II is pronounced thinning within that same area. Grade III is complete baldness within it. Unlike the Norwood scale, it describes diffuse thinning with the frontal hairline preserved.
At what stage is it too late to treat?
There is no published cut-off point, and anyone who gives you one is guessing. The most useful real-world marker we found is that HairMax limits the indication for its FDA-cleared devices to Norwood-Hamilton IIa to V in men and Ludwig I to II in women. That is a manufacturer defining the range in which it is prepared to claim its own product works.
Can you reverse Norwood 3?
The trials that support the approved drugs enrolled men with mild to moderate loss, and they measured hair count in a small marked area rather than reversal of a stage. Neither approved drug is documented to move someone from one Norwood stage back to a previous one. Treating earlier means more follicles are still cycling.
Do women get a Norwood pattern?
Some do. The Ludwig scale describes the common female pattern – diffuse thinning over the crown with the frontal hairline kept – but not every woman follows it, and some show frontal recession closer to the male pattern. That is one reason the Savin scale was later introduced, adding a separate assessment for frontal recession.
Does the scale change what treatment I get?
It can change what a device is cleared for and what a trial’s evidence covers, and it is a way for you and a clinician to track change over time rather than argue about whether a photograph looks different. It is a description, not a prescription.
Sources
- Gupta M, Mysore V. Classifications of patterned hair loss: a review. J Cutan Aesthet Surg. 2016. jcasonline.com
- Hamilton JB. Patterned loss of hair in man: types and incidence. Ann N Y Acad Sci. 1951;53:708-728. Modified by Norwood OT. South Med J. 1975;68:1359-1365.
- Ludwig E. Classification of the types of androgenetic alopecia (common baldness) occurring in the female sex. Br J Dermatol. 1977;97:247-254.
- Savin RC. J Invest Dermatol. 1992;98:604.
- HairMax. PowerFlex 272 Laser Cap product and clearance information. hairmax.com (checked 8 September 2026)
- U.S. Food and Drug Administration. PROPECIA (finasteride) tablets, prescribing information. 2022. accessdata.fda.gov
- Kaufman KD, Olsen EA, Whiting D, et al. Finasteride in the treatment of men with androgenetic alopecia. J Am Acad Dermatol. 1998;39(4 Pt 1):578-589. PMID 9777765.
- U.S. Food and Drug Administration. Women’s ROGAINE 5% Minoxidil Topical Aerosol, Drug Facts label. 2019. accessdata.fda.gov
Affiliate disclosure: this page contains affiliate links. We may earn a commission when you buy through them, at no additional cost to you. Commissions never determine what we cover or what the evidence sections say. Read our full affiliate disclosure.
How we researched this: every figure on this page is sourced to a numbered reference below. For this article those sources are the original Hamilton, Norwood, Ludwig and Savin classification papers as summarized in a peer-reviewed review, FDA drug labeling, and published manufacturer clearance information. Where a figure could not be verified from a primary source, we say so in the text rather than estimating. We do not test products and we do not practice medicine. See our review methodology.
