Hair loss on weight loss medicines: why it happens and when it stops

SASian Anderson, Writer and editor, MyGLP. Sources checked 21 October 2026.

What the trials found

Hair loss is listed as a common side effect on the NHS tirzepatide page and in the Wegovy leaflet, which adds that it may be more frequent at the 7.2mg dose. In the SURMOUNT-1 tirzepatide trial, hair loss was reported by about 5% of people on the highest dose against about 1% on placebo. In the STEP 1 semaglutide trial the figures were about 3% against 1%.

The pattern matters more than the percentage. People who lost the most weight, fastest, reported it most. That points at the weight loss rather than the molecule.

Telogen effluvium

Each hair on your head grows for two to six years, rests for about three months, then falls out and a new one grows. At any time about 10% of hairs are resting. A shock to the body, which includes a large drop in calories, childbirth, surgery or a bad illness, pushes a much bigger share into the resting phase at once. Three months later they all shed together. That is telogen effluvium. The NHS hair loss page lists weight loss among its causes and says this type of loss grows back.

The timing catches people out. The shedding starts around month three to four, when the weight loss is going well and the medicine seems to be the obvious culprit. It then runs for a few months and stops as the cycle resets. Full thickness takes six to twelve months after the shedding ends.

What you can check

• Iron. Low ferritin is the most common fixable cause of hair shedding in women, and heavy periods drain it. Ask your GP for a full blood count and ferritin. Our iron guide explains the numbers.
• Protein. Hair is made of protein. If you are eating a few hundred calories a day with little protein, hair is low on the body's list. The protein guide shows how to get 1.2 to 1.6g per kg on a small appetite.
• Thyroid. An underactive thyroid thins hair and is common in women. A TSH blood test is cheap and quick. See the thyroid guide.
• Zinc and vitamin D. Both are low in a fair number of UK women. A GP can test them if the shedding is heavy.
• Medicines. The combined pill, some blood pressure tablets and some antidepressants can add to shedding. Tell your GP everything you take.

What does not help

Expensive hair gummies, with no deficiency to fix, do nothing the food on your plate does not. Biotin supplements can interfere with thyroid and other blood tests, so stop them a few days before any test. Minoxidil lotion, which the NHS mentions for pattern hair loss, is not the answer to telogen effluvium either, since the hair is coming back on its own.

Slowing the shed

Slower weight loss means a smaller shock. The medicines are built to step up every four weeks, but your prescriber can hold you at a step for longer if you ask. Eating enough, and above all enough protein, is the single most useful thing. Be gentle with the hair you have: no tight ponytails, less heat, and a wide-tooth comb on wet hair.

When to see a GP

Hair loss in patches, a sore or scaly scalp, loss of eyebrows or body hair, or shedding that goes on past six months all need a GP. So does shedding that comes with tiredness, feeling cold, or heavy periods, since those point at iron or thyroid rather than the weight loss.

Sources

1. Hair loss (NHS)
2. Tirzepatide: side effects (NHS)
3. Wegovy patient information leaflet (Novo Nordisk, via the electronic medicines compendium)
4. Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1) (Jastreboff et al, New England Journal of Medicine, 2022)
5. Once-weekly semaglutide in adults with overweight or obesity (STEP 1) (Wilding et al, New England Journal of Medicine, 2021)