This information is for people who have high blood pressure. It tells you about taking potassium supplements. It is based on the best and most up-to-date research.
Do they work?
If you have high blood pressure, taking potassium supplements each day might help to lower it, but only by a small amount.
If you have high blood pressure you are more likely to have a heart attack or a stroke. But we don't know if taking potassium supplements reduces these risks. No studies have looked at this.
What are they?
Potassium supplements are tablets that you can buy over the counter from a pharmacy or from a health food shop. The label might say potassium chloride.
Your body needs potassium to help balance the amount of water in your blood and body tissues, and to help your nerves and muscles work properly.
Foods high in potassium include bananas, grapefruit, oranges, tomatoes, prune juice, and melons. 
It's important that you don't eat a lot of foods high in potassium if you are taking a potassium supplement. Too much potassium can be dangerous and affect the way your heart works. Talk to your doctor if you're worried about how much of these foods to eat.
Also, grapefruit and grapefruit juice contain a substance that can slow down the break up of some medicines by the body, including some medicines used to treat high blood pressure. This can increase the amount of the medicine in your blood. Other fruit and juices do not have this effect. Speak to your doctor if you're not sure whether you should be eating grapefruit or drinking grapefruit juice.
How can they help?
Taking a potassium supplement every day may help to lower your blood pressure.
Some studies have shown that taking about 2 to 3 grams of potassium each day can reduce your systolic pressure (the top number in your blood pressure reading) by 2 to 4 points, and your diastolic pressure (the bottom number) by around 2 points.   (To find out more about the numbers, see Understanding your blood pressure reading.)
You need to eat about five bananas a day to get this much potassium.
No studies have shown that taking potassium supplements reduces your risk of getting heart disease or kidney disease, or having a stroke.
How do they work?
People whose diets are low in potassium are more likely to have high blood pressure than people whose diets contain a lot of potassium. This is why doctors have looked at whether taking potassium supplements might help to lower blood pressure.
We don't know for sure how increasing the potassium in your diet might lower your blood pressure.