People who have been prescribed a common heart medication should watch out for serious red flag signs of issues with their blood and kidneys. There is an alert on the NHS website to call 111 if patients start noticing yellow skin or "10-minute nosebleeds".

Propranolol is a 'beta blocker' drug, according to NHS guidance, designed to treat heart problems, help with some of the symptoms of anxiety and prevent migraines. The medicine, only available on prescription, slows down your heart rate and makes it easier for your heart to pump blood around your body.

It's usually prescribed for high blood pressure and other heart problems. But it can also help with the physical symptoms of anxiety, like sweating and shaking. The British Heart Foundation reported that there are more than 50 million prescriptions for beta blockers in the UK each year, which includes propranolol.

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Typically, this tablet is taken once a day and is available in a standard or slow-release form. People may experience side effects, especially when they first start to take propranolol.

The NHS says: "Like all medicines, propranolol can cause side effects in some people, but many people have no side effects or only minor ones. Side effects often improve as your body gets used to the medicine."

• headaches
• feeling tired, dizzy or weak
• cold fingers or toes
• feeling or being sick (nausea or vomiting), or diarrhoea
• stomach pain

Most adults and children aged 12 and over can take propranolol, but there are a few exceptions to that rule. Doctors should be made aware if patients have had conditions such as low blood pressure, heart failure, depression or diabetes before, as this could influence dosage or finding an alternative medication altogether.

If you are taking it once a day, your doctor may advise you to take your first dose before bedtime, as it can cause dizziness. After the first dose, if you do not feel dizzy, take propranolol in the morning.

On occasion, the medicine can trigger some more serious side effects, with patients urged to "tell a doctor or call 111 straight away". The NHS says patients should look out for the following red flags of liver issues:

• The whites of your eyes turn yellow.
• Your skin turns yellow - although this may be less obvious on darker skin tones.
• You have pale poo or dark urine.

Alternatively, the NHS warned that some people might experience "low numbers of platelets in your blood", also known as thrombocytopenia. Those taking propranolol may find themselves having "nosebleeds that last for more than 10 minutes", have unexplained bruising, or find that they bruise more easily than usual.

Don't suddenly stop taking propranolol without talking to your doctor first, because it could cause serious heart issues like chest pain or even a heart attack. Some common side effects are feeling tired, dizzy, or weak; having cold hands and feet; trouble sleeping; and an upset stomach.

Serious side effects are rare, but they can occur. These include difficulty breathing, swelling in the face or throat, rapid weight gain, or an irregular heartbeat. If you experience any of these symptoms, seek medical attention immediately.

Propranolol might not be right for people with certain health issues, like asthma, uncontrolled heart failure, very low blood pressure, or diabetes, because it can hide the signs of low blood sugar. Make sure to tell your doctor about all the medicines, vitamins, and herbal products you are using, since propranolol can interact with other drugs, including some antidepressants and NSAIDs like ibuprofen.