Image copyright Getty Images

Giving blood is something that comes with a lot of rules.

But there are also a lot of myths and half-truths that people believe.

The number of men giving blood has dropped by 24.8% over the past five years, and the number of women giving blood has dropped by 6%, according to NHS Blood and Transplant (NHSBT).

They're asking for more donors - and the chances are you're eligible.

So what actually are the rules around giving blood?

There's no ban on veggies giving blood

Myths around blood donation are something NHSBT is used to dealing with - and a few years ago a survey was commissioned to find out what misconceptions people had.

It found that 3% of the more than 2,000 adults they asked thought being vegetarian could stop people from donating.

The concern comes down to iron - a key component in blood - and a worry that vegetarian diets contain less of it.

If your blood is low in iron, you won't be allowed to donate for your own safety.

But as long as you follow a well-balanced diet you should get enough iron in your body.

If you've got tattoos and piercings, you're not automatically banned

You can still give blood if you get a tattoo or a piercing, contrary to what 20% of people surveyed by NHSBT believed.

There is a rule though: you have to wait four months from the date of your tattoo or piercing before donating.

Image copyright Getty Images Image caption Make sure you know when you got your last tattoo before you try to give blood

And if you give blood between four months to a year after having a tattoo or piercing, staff at the donation centre might have a few extra safety checks to do.

Don't worry, there isn't a limited amount of blood in your body

The average adult has around 10 pints of blood in their body.

Making a donation uses about one pint, and your body works quickly to replace all the fluids and cells that have been lost. The blood you've donated is usually replenished within 24 hours.

Your body is incredible - it can make around 2m new red blood cells every second, according to NHSBT.

If you've been sick, you might need to wait a while

You should be completely recovered from any infection for at least 14 days before giving blood - and if you've been on antibiotics you'll have to wait seven days after finishing your medication before donating.

If you're on specific medical treatment, check with your local blood donation centre to see if you're eligible to give blood.

The rules around sex are less complicated than you might think

You can give blood without a waiting period unless...

You're a man who's had sex with another man in the last three months.

Image copyright Getty Images Image caption There are rules for gay men which make it more complicated to donate blood

You've had sex with a partner who's injected any type of drugs within the last three months.

You're a sex worker - although you may be accepted if you've not received money or drugs for sex in the past three months.

To sum up, you can donate blood if...

You are fit and healthy

Weigh between 7 stone 12 lbs and 25 stone (or 50kg and 160kg)

Are aged between 17 and 66

Are over 70 and have given blood in the last two years

You can find the full list on who's eligible to give blood here.

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