The hair growth cycle — why hair care takes 3–6 months, and when to see a doctor

Each hair has a life of its own: it grows, rests and sheds so a new one can replace it. Understanding the cycle answers the two most common questions — "why no change yet?" and "how much shedding is too much?"

The three phases

• Anagen — growth. The follicle divides and pushes the hair out at about 1 cm a month for 2–7 years, which sets how long your hair can get. Around 85–90% of scalp hairs are here [1][2].
• Catagen — transition. A brief 2–3 week pause while the follicle stops producing and shrinks [1][2].
• Telogen — rest. The hair sits for about 3 months before shedding while a new hair forms beneath it. Around 10–15% of hairs are here, which is where the normal 50–100 hairs a day come from [1][2].

Crucially, follicles are not synchronised, so in health there is never a moment when the whole head sheds at once [2].

Why 3–6 months

Whatever changes — nutrition, illness or any kind of care — shows up on the cycle's schedule, not ours. A hair shed today entered rest 2–4 months ago [3], and a hair that starts forming today needs about 3 months to clear the scalp and several more to be long enough to notice [1]. That is the biological reason any assessment of hair care needs at least 3–6 months, and why a product promising results in two weeks is arguing with the hair cycle itself.

When the cycle is disrupted: telogen effluvium

The most common cause of diffuse shedding is telogen effluvium — many hairs pushed into rest together after a trigger such as high fever, surgery, childbirth, rapid weight loss, severe stress or certain medicines. Shedding peaks 2–4 months later and usually settles within 6–12 months once the trigger is gone [3]. Iron deficiency, thyroid disorders and inadequate nutrition are correctable triggers worth testing for if shedding lasts beyond 6 months [3][4].

When to see a doctor

Hair loss has many causes, and some have medical treatments that work better when started early [5]. See a dermatologist or hair specialist if:

• Shedding stays above normal for more than 6 months, or you notice more visible scalp, a widening parting or a receding hairline
• Hair falls in round patches or from one area
• The scalp is red, itchy, scaly, sore or has pustules — these need prompt assessment, as some conditions scar the follicle permanently if left [5]
• You also feel very tired, your weight is changing quickly or periods are irregular
• You have started a new medicine or have a relevant medical condition

Doctors commonly check ferritin, thyroid function and vitamin D — all correctable [3][4] — and the earlier the cause is found, the more options you have.

Hair care means giving the cycle time. U-TURN: one capsule a day with the first meal of the day, or whichever meal suits you (biotin, zinc and selenium contribute to the maintenance of normal hair, for people who do not get enough from food each day) · ONE PEN conditions the scalp and hair roots · less breakage when combing · hair looks fuller and weightier · Review at month 6, and if you are still concerned, see a specialist to find the cause.