It was announced on Wednesday (7 April) that those aged under 30 in the UK are to be offered an alternative Covid vaccine to the AstraZeneca jab, due to emerging evidence linking it to rare blood clots.
But what exactly is a blood clot, how do they occur and what are the signs and symptoms to look out for?
Here’s what you need to know.
What are blood clots?
Although clotting is a necessary process that can prevent you from losing too much blood, for example when you get injured or cut, when a clot forms inside one of your veins it won’t always dissolve on its own, which can then be a potentially dangerous situation.
Although Healthline says that an immobile blood clot “generally won’t harm you,” there is a chance it could become dangerous if it moves and then travels to your heart and lungs.
The NHS says that blood clots “are rare in young, healthy people,” but you're more likely to get them if you:
- are staying in or recently left hospital – especially if you cannot move around much (like after an operation)
- are overweight
- are using combined hormonal contraception such as the combined pill, contraceptive patch or vaginal ring
- have had a blood clot before
- are pregnant or have just had a baby
- have an inflammatory condition such as Crohn’s disease or rheumatoid arthritis
What are the symptoms of a blood clot?
Symptoms of a blood clot include:
- throbbing or cramping pain, swelling, redness and warmth in a leg or arm
- sudden breathlessness, sharp chest pain (may be worse when you breathe in) and a cough or coughing up blood
“Blood clots can be life threatening if not treated quickly,” said the NHS.
You should get urgent advice from 111 if you think you have a blood clot. 111 will tell you what to do and they can arrange a phone call from a nurse or doctor if you need one.
However, you should call 999 or go to A&E if:
- you're struggling to breathe
- someone has passed out
This could be a blood clot in the lungs - known as a pulmonary embolism - which needs to be treated immediately.
What can I do to prevent blood clots?
According to the NHS, “Blood clots can be very serious and need to be treated quickly”, but “staying healthy and active can help prevent them.”
The NHS says there are certain things you can do to help avoid clots, including:
- staying active – taking regular walks can help
- drinking plenty of water to avoid dehydration – you're more likely to get a clot if you're dehydrated
- trying to lose weight if you're overweight
- wearing flight stockings or flight socks to improve your blood flow on long flights – a pharmacist can advise you about this
You should also avoid sitting for long periods without moving - if you can avoid it - try to avoid drinking a lot of alcohol as this can make you dehydrated, and avoid smoking, the NHS said.