All about diuretics

Doctors hand out millions of prescriptions for diuretics in the UK every year - used correctly, they reduce hospital admissions and save lives. But they do need monitoring with checks on your kidney function and blood pressure, to make sure we've got the balance right.

Your blood pressure is the pressure inside your arteries - the blood vessels that carry blood round your system, delivering vital oxygen and other nutrients to your organs. Your arteries are part of a closed system. Blood is pumped out by the heart into your arteries, goes to your organs and comes back to your heart through your veins.

If you increase the amount of fluid in a closed system, it increases the pressure - like putting more air in a balloon. Like a balloon, the walls of your arteries are stretchy - to an extent they can get bigger, making the blood vessels bigger and lowering the pressure inside them. But as you get older the artery walls get stiffer and less flexible.

High blood pressure and diuretics

As you get older, you get more prone to high blood pressure - being overweight, lack of exercise, excess alcohol, kidney disease and an unhealthy diet also put you at risk. High blood pressure is one of the biggest causes of heart attack and stroke. You may be more likely to get high blood pressure if it runs in your family or if you're of Afro-Caribbean origin. Lowering your blood pressure, with tablets like diuretics and calcium-channel blockers (which relax your blood vessels) helps in a huge way in cutting your risk of both.

How much salt you have in your diet plays a huge role in high blood pressure, too. As a nation, we eat about 9 g a day of salt - we should be aiming for no more than 6 g. Much of the salt in our diet is 'hidden' in processed foods like bread, ready meals and sauces. By cooking from scratch, you can monitor the salt in your diet more closely and keep your intake down.

If you want the taste of salt, try a reduced sodium alternative such as LoSۚalt®, which has two thirds less harmful sodium than normal table salt. Ideally, use this as a halfway house - if you reduce your salt intake over a few weeks, your taste buds will gradually adapt and you'll find your old foods far too salty. Herbs, spices and lemon juice can also perk up your food without adding to your salt intake.

The amount of fluid in your system is largely controlled by your kidneys. If you're dehydrated, for instance, the kidneys reabsorb more water, so you pass less urine. This keeps the amount of water and sodium in your blood constant.

How do diuretics work?

Diuretics are often known as 'water tablets' because they make you pass more urine. They work on your kidneys to increase the amount of urine you produce. Most of them do this by reducing the amount of salt your kidneys reabsorb into your bloodstream. Salt in your urine draws water with it, leaving less behind in your blood vessels. This is turn lowers your blood pressure. - as does relaxing the walls of your blood vessels, which some blood pressure tablets do.

Another complication of too much fluid in your system is heart failure. This is a condition where your heart can't pump fluid out around your system as fast as it comes back through your veins. This leads to a build-up of fluid in your ankles and lungs, causing shortness of breath when you exercise or lie flat. Not surprisingly, diuretics are a mainstay of treatment for the symptoms of heart failure, too.

Diuretics can cause side effects - including making you rush to the loo. Taking them in the morning stops your sleep being disturbed, and you might want to delay your dose if you're going out and won't be near a toilet for a couple of hours. They can affect the levels of sodium and potassium in your system, leading to tiredness, weakness and abnormal heart rhythms. If you're taking them, you'll need blood tests at least yearly to check these levels. They can drop your blood pressure too much, causing light-headedness or dizziness on standing. If in doubt, speak to your doctor - but don't stop them without medical advice. You've been given them for a reason!

With thanks to 'My Weekly' magazine where this article was originally published.

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. Patient Platform Limited has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.