Causes of Hair Loss and Treatments That Actually Work

Hair loss is one of those problems that people throw a lot of money at without fully understanding what is causing it. The supplement aisle alone has dozens of products claiming to grow thicker, longer hair. Most of them are not doing what the label implies.

This guide covers the actual mechanics of hair loss, which treatments have clinical research behind them, and what is mostly marketing noise.

How Hair Growth Works

Each hair follicle goes through a cycle with three main phases. The anagen phase is active growth, lasting two to seven years on the scalp. The catagen phase is a short transitional period. The telogen phase is rest, after which the hair sheds and the cycle starts again. At any given time, roughly 85 to 90 percent of scalp hairs are in the anagen phase.

The length your hair can grow is largely determined by how long your anagen phase lasts, which is mostly genetic. This is why some people can grow hair to their waist without trying while others seem to hit a ceiling at shoulder length no matter what they do.

What Causes Hair Loss

Androgenetic Alopecia (Pattern Hair Loss)

This is the most common form of hair loss in both men and women. It is driven by genetics and hormones, specifically the effect of dihydrotestosterone (DHT) on hair follicles. DHT is derived from testosterone via an enzyme called 5-alpha reductase. In people who are genetically susceptible, DHT binds to receptors in hair follicles and gradually causes them to shrink, producing thinner, shorter hairs over time until they stop producing hair entirely.

In men, this presents as a receding hairline and thinning at the crown. In women, the pattern is typically diffuse thinning across the top of the scalp with the hairline generally preserved.

Telogen Effluvium

This is a temporary, diffuse shedding caused by a disruption to the hair cycle. Common triggers include significant physical stress like surgery or illness, childbirth, rapid weight loss, severe emotional stress, thyroid dysfunction, and certain medications. The shedding typically starts two to four months after the triggering event and resolves once the trigger is addressed.

It is worth knowing about because it is frequently mistaken for permanent hair loss. People notice heavy shedding and panic, but in most cases telogen effluvium reverses on its own over six to twelve months.

Nutritional Deficiencies

Iron deficiency is the most well-established nutritional cause of hair loss, particularly in women. Low ferritin levels (the stored form of iron) are associated with increased shedding even when hemoglobin levels are normal. Zinc deficiency and severe protein deficiency can also contribute. Vitamin D deficiency has been linked to alopecia areata in some studies.

Treatments With Real Evidence

Minoxidil

Minoxidil is one of two FDA-approved treatments for hair loss. It was originally developed as a blood pressure medication and hair growth was discovered as a side effect. Applied topically to the scalp, it works by widening blood vessels and prolonging the anagen (growth) phase of the hair cycle. It does not block DHT.

It is available over the counter in 2% and 5% concentrations. The 5% foam is generally more effective and better tolerated. Results take four to six months to appear and require continued use. Stopping minoxidil leads to gradual return of hair loss over several months. It works for both men and women, though oral minoxidil (at low doses like 0.25mg to 2.5mg) has become increasingly popular as an alternative with good evidence.

Finasteride (Men Only)

Finasteride is a 5-alpha reductase inhibitor. It blocks the conversion of testosterone to DHT, reducing scalp DHT levels by roughly 60 to 70 percent. This is the most direct treatment for androgenetic alopecia because it addresses the hormonal mechanism causing the problem.

In studies, about 80 percent of men who took finasteride for twelve months showed improvements in hair count or no further loss. It is prescription-only and not recommended for women of childbearing age because of risks to male fetal development. Potential side effects include sexual dysfunction in a small percentage of users, which is the most common reason people discontinue it.

Ketoconazole Shampoo

Ketoconazole is an antifungal with mild DHT-blocking properties. A 1% to 2% ketoconazole shampoo used two to three times per week has shown modest benefits for androgenetic alopecia in a few studies. It is significantly weaker than finasteride but has essentially no systemic side effects when used topically. It is a reasonable addition to a hair care routine rather than a standalone treatment.

Scalp Massage

A Japanese study found that standardized scalp massage for four minutes daily increased hair thickness after 24 weeks. The proposed mechanism is that mechanical stimulation increases blood flow and stretches follicle cells, which may encourage the anagen phase. It costs nothing and has no downsides. It is not going to reverse significant hair loss on its own, but it is a legitimate supporting habit.

The Biotin Question

Biotin (vitamin B7) is probably the most aggressively marketed hair supplement available. It is in nearly every hair, skin, and nail product on the market.

The honest picture: a 2024 review published in the Journal of Clinical and Aesthetic Dermatology examined the available research and found that the highest-quality controlled study showed no difference between biotin and placebo groups for hair growth. The other qualifying studies were methodologically weak. The conclusion was that biotin supplementation is not supported by strong evidence for people without an actual deficiency.

If you have a documented biotin deficiency, supplementation is appropriate and beneficial. But most people eating a reasonably balanced diet already meet the daily requirement through food. The gap between biotin's reputation and its evidence base is significant.

What Actually Supports Healthy Hair Growth

Adequate protein intake matters because hair is almost entirely made of keratin, which requires amino acids. People on very low calorie or very low protein diets often experience increased shedding. Aiming for sufficient dietary protein rather than supplements is the more reliable approach.

Iron levels deserve attention, particularly for women. A blood test checking ferritin alongside standard hemoglobin gives a more complete picture of iron status. If ferritin is below 30 to 40 ng/mL, addressing that deficiency through diet or supplementation is worth doing before attributing shedding to other causes.

Reducing mechanical stress on the hair matters more than most people realize. Tight hairstyles, excessive heat styling, rough towel drying, and chemical treatments all physically damage the hair shaft and cause breakage that looks like thinning even when the follicles themselves are healthy.

When to See a Doctor

Sudden or patchy hair loss warrants a dermatologist visit. Alopecia areata, an autoimmune condition causing circular patches of hair loss, requires different treatment than androgenetic alopecia. Scarring alopecias, which permanently destroy follicles, need early diagnosis to limit damage.

If you are experiencing diffuse shedding that has lasted more than six months without an obvious trigger, blood work checking thyroid function, iron levels, and hormones is a reasonable starting point before spending money on supplements or topical treatments.

The bottom line: minoxidil and finasteride are the treatments with the strongest evidence. Everything else is either supportive, situational, or overhyped. Starting with the fundamentals, nutrition, scalp health, and reducing physical damage, and adding clinical treatments where appropriate is a better approach than chasing supplement trends.