A doctor has urged people to check one thing on their phone every day to lower their risk of a deadly disease that kills more than 3,000 people in the UK every year. NHS surgeon, Doctor Karan Rajan - who is best known online as Dr Raj, issued a warning to prevent people from developing skin cancer.

According to Dr Raj there is a way to check on your mobile phone whether you need to apply sun cream that day.

He explained that weather apps will tell you the ultraviolet (UV) index for the day, with certain levels needing extra caution in order to keep the skin healthy.

Speaking on social media platform TikTok, he explained: “I found out only this year that you can look at the UV index on your mobile phone. If you go on your weather app, it gives you the UV index for the day on your phone.”

Wearing sunscreen can not only help protect against cancer but also reduces the appearance of ageing, he said.

“The issue about sunscreen is there's two things, right?” Dr Raj continued.

“UV rays increasing your risk of cancer versus UV rays increasing the risk of photo ageing and just aesthetic damage.”

He warned that if you are fair skinned you will need to apply sunscreen on a daily basis - or if the UV index is at around three.

Dr Raj said: “Now, if I didn't care about photo ageing and the sun making you look older and I only cared about the skin cancer, if I'm in the UK where it's probably UV index three, most of the year, do I need to wear sunscreen every day?

“Probably not right. But if someone, you know, like a Caucasian person - probably, yes, they should wear sunscreen on a daily basis for the skin cancer protection UV index of three or more.”

However, if you have darker skin he said you might only need to apply sunscreen when the index is higher.

“Like for me, for example, maybe I should only be considering wearing sunscreen if the UV index was maybe more than seven or eight, and I was in the sun for a prolonged period of time,” Dr Raj added.

The values of the UV index range from zero upward. The World Health Organisation (WHO) explains that the higher the UV index, the “greater the potential for damage to the skin and eye, and the less time it takes for harm to occur”.

It says: “A marked increase in the incidence of skin cancer in fair-skinned populations worldwide is strongly associated with excessive UV radiation exposure from the sun and possibly artificial sources such as sunbeds.

“Current evidence indicates that personal habits in relation to sun exposure constitute the most important individual risk factor for UV radiation damage.”

The WHO issued this advice regarding the UV index:

• Zero to two - You can safely enjoy being outside
• Three to seven - Seek shade during midday hours. Slip on a shirt, slop on sunscreen and slap on a hat
• Eight and above - Avoid being outside during midday hours. Make sure you seek shade. Shirt, sunscreen and hat are a must.

It adds: “Even for very sensitive fair-skinned people, the risk of short-term and long-term UV damage below a UVI of two is limited, and under normal circumstances no protective measures are needed.

“If sun protection is required, this should include all protective means, i.e. clothing, hat and sunglasses, shade and sunscreen.”

Cancer Research UK says that skin cancers can look “very different” and the symptoms will vary.

However, it lists common symptoms of skin cancer as a sore or area of skin that:

• Doesn't heal within four weeks
• Looks unusual
• Hurts, is itchy, bleeds, crusts or scabs for more than four weeks.

You should speak to your GP if you have any of these symptoms or are worried about any abnormal areas of skin.