Which Diuretic Is Right For Your High Blood Pressure?

If you have been diagnosed with high blood pressure, your doctor will likely recommend you take a type of medication called a diuretic. While some patients can keep their blood pressure down with lifestyle changes alone, most need medication. Diuretics, also known as water pills, can be a very effective treatment for high blood pressure.

How do diuretics work?

Diuretics work by causing your kidneys to release more sodium into your urine, which helps your body get rid of excess sodium and water. This lowers your blood pressure by reducing the amount of fluid in your blood, allowing it to be more easily transported through your arteries and veins. They also help to relax the walls of your blood vessels.

Since sodium pulls water into your blood, limiting salt intake is recommended for most individuals, as we tend to consume too much sodium in our diets. Diuretics and a low sodium diet complement one another to help lower blood pressure.

Types of diuretics

Three types of diuretics are commonly prescribed, which are discussed below. Each type affects your kidneys differently, so you may find that one works better for you than another. You may also be prescribed pills that are a combination of more than one type of diuretic, or a combination of a diuretic and other medication. Combination pills make it easier to keep track of your medications and are more convenient.

The three types of diuretics are:

Thiazide

Thiazide diuretics¹ are the most commonly prescribed diuretics. They work directly on the kidney and prevent sodium reabsorption, typically by 3 to 5%.

Three thiazide diuretics are approved for the treatment of high blood pressure and may be packaged under a specific name-brand:

• Hydrochlorothiazide

• Chlorthalidone

• Indapamide

Thiazide diuretics block a specific channel that carries sodium chloride and prevents its absorption. You take these diuretics as tablets in the morning with food. They are considered safe and effective, and most people respond well to them.

However, they can trigger sulfonamide allergy, and do have some known side effects, which include:

1. Potassium insufficiency — If you take thiazide diuretics, your doctor may advise you to increase your potassium intake by consuming more high potassium foods such as bananas, spinach, stone fruits, and winter squash.

2. Elevated blood sugar — The altered potassium-sodium balance can cause your pancreas to produce less insulin. Despite this, thiazide diuretics are still prescribed to people with type 2 diabetes² because the benefits outweigh the risks. Some studies indicate that chlorthalidone and indapamide have less impact than hydrochlorothiazide.

3. Elevated blood calcium levels (hypercalcemia) —This can cause bone fractures, kidney stones, a slowed heart rate, and high blood pressure. However, slight hypercalcemia can help promote bone health and reduce the risk of kidney stones.

4. Increased risk of developing gout — This is another issue to watch for when taking diuretics.

5. Risk of hyponatremia — A condition where there is too little sodium in your blood.

When you first go on thiazide, keep an eye out for symptoms such as confusion, seizures, muscle cramps and weakness, nausea, low energy, and headaches. Typically, this risk reduces as your body becomes used to the medication, but in some cases, these side effects can be severe enough to require hospitalization.

If you experience rare side effects from taking thiazide, you will likely be switched to another diuretic and may be given saline and restricted from drinking water until your blood returns to normal. 

Loop diuretics

Loop diuretics interfere with salt and water transportation in the "loop of Henle," which are structures that exist throughout your kidneys. These diuretics should be taken once a day, in the morning. They can cause similar side effects to thiazide diuretics, as they change the salt balance in your bloodstream.

Other side effects include:

• Dizziness on standing if blood pressure gets too low. This is rare in people with hypertension but can happen if you take multiple medications.

• Upset stomach

Potassium-sparing diuretics

Potassium-sparing diuretics are typically combined with another type of diuretic rather than being used on their own. A potassium-sparing diuretic reduces the potassium depletion that can come with other diuretics.  By using both kinds of diuretics, you can avoid losing too much potassium. However, sometimes this can result in blood potassium levels becoming too high.

There are two distinct subsets of potassium-sparing diuretics:

1. Amiloride and triamterene — As with other diuretics, they interfere with salt and water transportation in the kidneys, but they also block channels that excrete potassium to keep it in your body. 

2. Eplerenone and spironolactone — These block the action of aldosterone, which triggers your kidneys to retain fluid to encourage kidneys to excrete more fluid.

The side effects of potassium-sparing diuretics depend on the type used.

Amiloride and triamterene can cause:

• Stomach ache

• Dry mouth

• Dizziness or faintness when getting up

• Skin rash

• Drowsiness

• Confusion

• Headache

• Aches and pains

• Muscle cramps and weakness

• Diarrhea or constipation

• Elevated potassium levels

Spironolactone and eplerenone can cause:

• Upset stomach

• Nausea

• Sexual dysfunction

• Breast enlargement in men and women

• Irregular menstruation

• Confusion

• Dizziness

• Skin rash

• Excessive hair growth

• Liver problems

• Elevated potassium levels

If you take a potassium-sparing diuretic, be careful with salt substitutes, as many use potassium instead of sodium. This is particularly true if you are also on ACE inhibitors or angiotensin receptor agonists, both of which are commonly prescribed for high blood pressure.

Your doctor will likely prescribe you a thiazide diuretic first. They are generally effective and have the fewest side effects. If you are allergic to sulfonamide, you will be prescribed a loop diuretic. Your doctor will likely switch your medication or add a loop diuretic if thiazide is not working well or causing adverse side effects.

There are also other types of diuretics, but they are not typically used to treat high blood pressure.

Will diuretics make me need to use the bathroom more?

Yes. If you are using diuretics, you will produce more urine than before taking the medication. This is why your doctor will advise you to take them first thing in the morning, as the increased urination will wear off by the time you go to bed. You could adjust the time you take them if you work nightshifts, for example.

Be aware that if you consume any other substances that make you pee more, such as alcohol, you are very likely to become dehydrated. You should not drink heavily if taking diuretics (note that one of the primary causes of a hangover is dehydration).

Talk to your doctor about how much you can adjust the time you take your diuretic. For example, if you have a long early morning flight, you might want to wait until you land to avoid extra trips to the bathroom mid-flight and the dehydration caused by flying. However, you should not take a diuretic within six hours of bedtime.

This effect often decreases after you have been on the diuretic for a while as your body finds a balance, especially if you retain a lot of water. 

Over-the-counter diuretics

You might see over-the-counter diuretics in the pharmacy and wonder if they are an option for you.

First, these over-the-counter "diuretics" are either herbs or dietary supplements. They are advertised primarily to reduce bloating and "water weight," and are not regulated by the FDA. They are commonly taken for weight loss, to reduce period-related symptoms, and by bodybuilders³. However, they can cause adverse side effects, as some bodybuilders have collapsed from dehydration and/or high or low potassium due to using diuretics to "increase muscle definition."

You should not use over-the-counter diuretics to try and treat your high blood pressure. Many do not work, the dosage may not be standardized, and they can easily lead to health problems. 

Can you overdose on diuretics?

Yes. If you skip a dose, you should not take a double dose to "catch up." However, further research⁴ is needed on diuretic overdoses. If you have accidentally taken your diuretic twice, you should call your doctor. Overdosing on diuretics is generally not serious, but it can cause:

• Nausea

• Diarrhea

• Lethargy and weakness

• Dehydration

• Hypotension (too-low blood pressure)

Most diuretics can cause a significant drop in potassium if you take too much, which may cause muscle weakness, cramps, and an irregular heartbeat. Potassium-sparing diuretics can lead to too much potassium in the bloodstream, resulting in weakness, abdominal pain, diarrhea, heart palpitations, and chest pain.

If you overdose on diuretics, you will be treated with IV fluids and possibly other treatments to correct electrolyte imbalances. For example, as an overdose can cause hypernatremia, which results from too little sodium, saline would be administered. While diuretic overdose is not generally serious, it can be if you have weak kidneys or are prone to high potassium.

If you skip a dose, you should take it when you realize it, but not too close to your next dose. It is better to miss a dose than to double up.

What if I skip a dose?

Studies with intentional⁵ placebo substitution have demonstrated that missing a single dose is not a significant problem. While you should always take your medication as prescribed, forgetting a dose occasionally will not result in a significant loss of blood pressure control.

Can I stop taking diuretics?

Like other blood pressure medications, diuretics are generally taken for life. Just because your blood pressure is normal does not mean you can stop taking your diuretics. 

Stopping diuretics can cause rebound sodium and water retention⁶, potentially worsening your blood pressure. You should not stop taking diuretics without talking to your doctor unless you have an allergic reaction (in which case you should speak with your doctor right away).

Some people can be weaned off of blood pressure medication after making lifestyle changes, but these lifestyle changes have to be sustained, or blood pressure will get out of control again. 

The lowdown

If you have high blood pressure, your doctor is likely to prescribe diuretics if lifestyle changes aren’t enough to lower it.

Which diuretic is suitable for you depends on your biological makeup. Most people take a thiazide diuretic, which is generally well-tolerated and has long been used to treat high blood pressure. If you are allergic to sulfonamide, your doctor will prescribe a loop diuretic. Potassium-sparing diuretics are generally used alongside other diuretics to help keep potassium levels stable.

Do not take over-the-counter diuretic supplements to control blood pressure, as these are poorly regulated and unlikely to be effective.