Can dehydration cause hair loss?

Whether dehydration causes hair loss, whether drinking water helps hair grow, and the more likely causes of shedding and dry hair.

Written by Shuna Hammocks, consultant trichologist (IoT no. 10060)

Published 11 December 2024 Updated 10 October 2026

Illustration of a jug of water with lemon and mint and a glass

The short answer

There’s no good evidence that everyday mild dehydration causes hair loss, and drinking more water won’t make your hair grow faster. Being seriously unwell, with vomiting, a high fever or not eating, can trigger shedding a few months later, but that’s the illness, not the water. Hair that’s dry and brittle is usually down to how it’s treated, not how much you drink.

Does drinking water help hair growth?

Not directly. Your body needs enough fluid to work well, and the NHS suggests 6 to 8 glasses a day, but extra water beyond that does nothing more for your hair. Hair growth depends on your genes, hormones, diet and health.

What is more likely to be causing hair loss?

Telogen effluvium: shedding two to three months after illness, stress, surgery or a crash diet
Low iron, low B12 or a thyroid problem
Not eating enough protein
Male pattern hair loss or female pattern hair loss

What about dry, brittle hair?

Dry hair is about the hair shaft, not your fluid intake. Heat styling, bleach, sun, hard water and rough handling dry hair out and lead to breakage.

Hair loss with nail changes

Fine vertical ridges on the nails are common and become more so with age. Nails that are very soft, brittle, spoon-shaped or that change suddenly, along with hair loss, are worth mentioning to your GP, who may check your iron, thyroid and other levels.

If something isn’t right with your hair or scalp, a consultation is where I take your history, examine your hair and scalp closely and give you a written plan.