Hair loss is treated, in most conversations, as a single condition with a single solution. It is not. There are at least six distinct types of hair loss, each with its own mechanism, its own treatment pathway, and its own timeline for recovery.
The most expensive mistake you can make is beginning a protocol before you understand what you are treating. Finasteride does not help telogen effluvium. Iron supplements do not stop androgenetic alopecia. Starting the wrong treatment does not just waste time — in some cases it delays the correct diagnosis by months or years.
Identifying what you have is not a preliminary step. It is the treatment.
1. Androgenetic Alopecia
Androgenetic alopecia (AGA) accounts for over 95% of hair loss in men. It is driven by a hormone called dihydrotestosterone (DHT) — a potent androgen converted from testosterone by the enzyme 5-alpha-reductase. In people with a genetic predisposition, DHT binds to androgen receptors in scalp follicles and causes them to gradually miniaturise.
The process is slow and systematic. Affected follicles do not die — they shrink, producing progressively finer hairs until they produce nothing visible. This biology matters for treatment: miniaturised follicles that have not been dormant for long can often be reactivated.
Pattern: Receding hairline following the Norwood scale; thinning at the crown; sides and back typically spared.
Treatment: Finasteride (reduces DHT by 60–70%), minoxidil (prolongs growth phase), and their combination. See the full treatment guide →
Reversibility: High if treated early; moderate in established cases; lower once follicles have been dormant for years.
2. Telogen Effluvium
Telogen effluvium (TE) is the most commonly misdiagnosed form of hair loss.
Under normal conditions, approximately 10–15% of scalp follicles are in the telogen (resting) phase at any given time. A triggering event — significant illness, surgery, major psychological stress, extreme weight loss, childbirth, or nutritional deficiency — can force a large proportion of follicles into telogen simultaneously.
The result is a sudden, diffuse, often alarming wave of shedding that begins approximately 8–12 weeks after the triggering event. Because the timing gap is long, most people do not connect the shed to its cause.
The important truth about telogen effluvium: it is almost always reversible once the trigger is removed. The follicles are not damaged. They paused.
Pattern: Diffuse shedding across the whole scalp — not patterned recession. Often dramatic in volume.
Key diagnostic clue: A significant stressful event, illness, nutritional deficiency, or weight loss 2–3 months before shedding began.
Treatment: Identify and address the trigger. Blood tests to rule out nutritional causes. Time.
Reversibility: Typically high, within 6–12 months of the trigger resolving.
3. Alopecia Areata
Alopecia areata is an autoimmune condition. The immune system — for reasons that are not fully understood — misidentifies hair follicles as a threat and attacks them. The result is patchy, often sudden hair loss in circular or oval areas.
This is not hormonally driven. It is immunological. Standard AGA treatments (finasteride, minoxidil in isolation) are not appropriate first-line interventions. Alopecia areata requires an immunological approach and should be managed by a dermatologist.
Pattern: Distinct circular or oval patches of complete hair loss. Can affect the beard, eyebrows, and eyelashes as well as the scalp. No progressive recession pattern.
Variants: Alopecia totalis (complete scalp hair loss) and alopecia universalis (complete body hair loss) are severe extensions of the same autoimmune process.
Treatment: Intralesional corticosteroids, topical immunotherapy, JAK inhibitors (increasingly used for moderate-severe cases). Minoxidil can be helpful as an adjunct.
Reversibility: Variable. Patchy alopecia areata often resolves spontaneously or responds to treatment. Extensive or universal presentations are more difficult to treat consistently.
4. Nutritional Deficiency Hair Loss
Low ferritin (iron stores), vitamin D, zinc, or B12 can cause diffuse hair thinning without any discernible pattern. This is one of the most underdiagnosed contributors to shedding — primarily because standard laboratory “normal” ranges are not calibrated for hair health.
A ferritin level of 20 ng/mL will be labelled “normal” on most laboratory reports. For optimal hair follicle function, the target is 70 ng/mL or above. This gap between “not deficient” and “optimal” is where countless people find themselves stuck, unaware that their blood tests are not actually normal for hair purposes.
Pattern: Diffuse thinning without recession. Reduced density throughout. No Norwood-type pattern.
Key diagnostic clue: Blood tests that are “normal” but not optimal; vegetarian or restrictive diet; fatigue or other symptoms of deficiency.
Treatment: Address the specific deficiency. See the full blood test guide →
Reversibility: Fully reversible once deficiencies are corrected. Timeline: 3–6 months for blood markers to normalise; 6–12 months for visible hair recovery.
5. Diffuse Patterned Alopecia
Diffuse patterned alopecia (DPA) shares the same hormonal driver as AGA — DHT — but without the classic temple recession. Instead, thinning spreads across the entire scalp, with the centre part and vertex most visibly affected.
DPA is frequently confused with telogen effluvium because the shedding pattern appears global rather than patterned. The critical distinction is the cause: DPA is androgen-driven and requires the same DHT-blocking treatments as AGA. Telogen effluvium is event-triggered and resolves with time and trigger removal.
DPA is particularly common in women with androgenetic hair loss, where it presents as a widening centre part rather than the receding hairline pattern seen in men.
Pattern: Global thinning; widening part; increased scalp visibility throughout; no prominent temple recession.
Treatment: Same protocol as AGA — finasteride, minoxidil, microneedling. Women should be evaluated for hormonal contributors (PCOS, thyroid).
Reversibility: Moderate to high with early treatment; similar to AGA trajectory.
6. Retrograde Alopecia
Retrograde alopecia is the least-discussed but surgically most important form of hair loss on this list. It affects the sides and nape of the neck — areas that are typically considered the “safe donor zone” for hair transplants because follicles in these regions are normally DHT-resistant.
In retrograde alopecia, this assumption fails. Follicles in the donor zone have been sensitised and undergo miniaturisation along with the rest of the scalp. This has significant implications: follicles transplanted from an affected donor zone will eventually miniaturise in their new location, making the transplant progressively less permanent over time.
Retrograde alopecia does not require treatment in isolation — it requires identification. If you are considering a hair transplant, a specialist assessment specifically evaluating the donor zone for retrograde alopecia is essential.
Pattern: Thinning or recession at the sides and back of the scalp, beyond normal temporal recession.
Key diagnostic clue: Hair loss that appears to be progressing in the typically stable donor area.
Types Can Co-Exist
This is the most important practical point in this entire guide.
A person can simultaneously have:
- Androgenetic alopecia (the underlying genetic driver)
- Telogen effluvium (triggered by a recent stressful event)
- Nutritional deficiency (ferritin and vitamin D at suboptimal levels)
All three are contributing to shedding. Treating only the AGA component while the ferritin remains low and the stressor is unresolved produces incomplete results — and creates the misleading impression that AGA treatments are not working.
A thorough diagnosis identifies all contributing factors. Treatment addresses all of them.
Frequently Asked Questions
How do I diagnose my hair loss type? The most reliable approach combines three elements: your personal history (any recent stress, illness, weight changes, dietary changes, medications), a blood panel (ferritin, vitamin D, TSH, zinc, DHT), and a clinical scalp examination — ideally with trichoscopy — by a dermatologist. Pattern analysis alone is not sufficient.
Can I have two types of hair loss at once? Yes, and it is more common than most people expect. AGA with concurrent telogen effluvium is particularly common. Each contributing factor requires its own addressed treatment component.
Is alopecia areata hereditary? There is a genetic component — having a first-degree relative with alopecia areata increases your risk. But it is not deterministic in the way androgenetic alopecia is. Many people with a family history of alopecia areata never develop it.
Is androgenetic alopecia permanent? The genetic predisposition is permanent. But the hair loss itself — the miniaturisation of individual follicles — is a progressive process that can be slowed, halted, and in many cases partially reversed with appropriate treatment. The sooner treatment begins, the more follicular function can be preserved and recovered.