By Hannah Morrison
There's a warning over tanning injections being used people across the UK
A special Newsbeat investigation has uncovered a growing trend in people injecting themselves with an unlicensed tanning drug.
Melanotan hasn't been cleared to be used in the UK but some websites are selling it online.
The drug is a synthetic hormone that when injected stimulates the melanin that occurs naturally in the body.
Melanin is a pigment that determines how dark your skin is. The more of it you have, the browner you are.
Twenty-seven-year-old Stacey Boardman from Rochdale started using Melanotan two months ago.
She said: "About 40 friends I know are taking it. It makes you really brown quickly and you can control how dark you go. You don't get the streaks and it doesn't wash off."
We do not know if it works and we don't know how safe it is
Claire Tilston from the Medicines and Healthcare Regulatory Agency (MHRA)
Health workers at needle exchange units have told Newsbeat more and more people want syringes for use with Melanotan.
The concern is that testing hasn't finished on the drug and it hasn't been passed as safe for human use.
The government body responsible for regulating medicines is warning people not to take the risk.
Claire Tilston is from the Medicines and Healthcare Regulatory Agency (MHRA).
She said: "It has not been tested enough for its effectiveness or its safety.
"We do not know if it works and we don't know how safe it is.
"We do not know what side effects it may cause for people who use it or potentially what the long term effects on their health may be."
Because Melanotan hasn't been licensed for use in the UK, it is illegal to sell it.
But in the last month the MHRA has had to write to 18 companies asking them to stop advertising the drug for sale.
Many also offer the kit you need to take it, with syringes and sterile water.
Another concern is that users might not know how to safely inject themselves and the websites offering Melanotan don't give proper medical advice.
Sian Rowe, Nicola Boardman and sister Stacey all use the jab
Medicines regulator Claire Tilston says infections can be passed on easily.
She said: "It's a very complicated product to use and should not be used without proper advice."
But for Sian Rowe, 23, and Nicola Boardman, 21, the warnings are not enough to make them stop injecting.
They said: "I've got the tan that I want and have no side effects from it, so I'm happy with it."
"I'm only young and I feel fine on it and the tan looks great so I don't mind."
You can report anyone selling or advertising Melanotan anonymously to the MHRA information Centre on 020 7084 2000.