9 Olmesartan Side Effects and How to Manage Them

If you have high blood pressure, one treatment option your healthcare team may consider is olmesartan (Benicar). Olmesartan is an oral medication that causes your blood vessels to relax and widen, which lowers your blood pressure. Because of how it works, olmesartan is considered an angiotensin II receptor blocker (ARB).

ARBs like olmesartan can be a good option if you developed a persistent dry cough from similar medications known as angiotensin-converting enzyme (ACE) inhibitors. However, olmesartan also has unique side effects of its own to consider.

Olmesartan side effects at a glance

Most olmesartan side effects are mild and tend to improve over time. But in rare cases, serious side effects may require medical attention.

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Mild olmesartan side effects include:

• Dizziness

• Weakness

• Low blood pressure

• Vomiting

• Hair loss

• Back pain

• Headache

• Common cold symptoms

Less common but potentially serious olmesartan side effects include:

• Angioedema (swelling under the skin)

• Severe diarrhea

• High potassium levels

• Worsening kidney problems

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Below, we dive deeper into nine of these side effects and how to manage them.

1. Dizziness

The most common olmesartan side effect is dizziness. Since olmesartan can lower your blood pressure, you may feel dizzy as your body adjusts to this change.

If you feel dizzy, sit or lie down immediately to prevent falls and potential injuries. Stand up slowly after the dizziness passes, allowing your body time to adjust to the change in position.

If your dizziness persists or becomes severe, contact your prescriber. It’s possible that olmesartan may be lowering your blood pressure too much, which is called hypotension. More on that later.

2. Weakness

Another potential olmesartan side effect is weakness. Similar to dizziness, weakness may be due to olmesartan lowering your blood pressure. In most cases, this should get better as your body gets used to the medication.

But if you experience weakness that gets worse or doesn’t go away, contact your prescriber right away. It’s possible that your potassium levels may be too high, which can cause symptoms such as weakness, fatigue, and tingling or numbness.

3. Vomiting

Some people have reported vomiting while taking olmesartan. You can take olmesartan with or without food. But if it upsets your stomach, try taking it with food. Eating smaller, more frequent meals rather than large meals may also help if you’re feeling queasy.

Persistent vomiting can lead to dehydration and electrolyte imbalances. So it’s best to seek medical care if your vomiting doesn’t seem to be letting up. Vomiting with severe diarrhea can also be a symptom of certain intestinal problems caused by olmesartan. Contact your prescriber right away if these symptoms develop.

4. Hair loss

Hair loss or thinning is a rarely reported olmesartan side effect. If you notice hair loss after starting olmesartan, talk to your prescriber. They can help determine whether the hair loss is likely due to the medication or a different cause.

5. Low blood pressure

Another potential side effect of olmesartan is hypotension, or low blood pressure. Symptoms of low blood pressure include dizziness, fatigue, and blurred vision. As mentioned above, you may experience some of these symptoms as your body adjusts to the change in blood pressure. But it’s still a good idea to tell your care team if they’re happening.

Your healthcare team will monitor your blood pressure regularly while you're taking olmesartan to ensure you’re on the right dosage. They may also have you check your blood pressure at home. Let them know if your readings are frequently below your target range.

Symptoms such as cold and clammy skin, rapid breathing, and a weak pulse can mean your blood pressure is dangerously low. In this case, have someone call 911 or take you to the nearest ER.

6. Angioedema

Although rare, angioedema is a serious olmesartan side effect. It involves swelling of the deep layers of your skin, often occurring in the face, lips, tongue, or throat. Angioedema can be life-threatening if it affects your breathing.

If you experience any facial swelling after taking olmesartan, seek immediate medical attention. This is not a side effect to ignore or try to manage on your own. If angioedema affects your throat or tongue, it can block your airway and quickly become a medical emergency.

If you experience this side effect, your prescriber will likely have you stop taking olmesartan and provide you with an alternative treatment option.

7. Severe diarrhea

Olmesartan can cause intestinal problems resulting in severe, chronic diarrhea, but this is rare. This side effect can develop at any point during treatment. Along with diarrhea, you may notice symptoms such as weight loss, abdominal pain, and nausea and vomiting.

Severe diarrhea can cause dehydration, which can be dangerous if it's not treated promptly. Symptoms of dehydration include increased thirst, less frequent urination, and headache. If you develop severe diarrhea while taking olmesartan, contact your prescriber right away.

8. High potassium levels

High potassium levels are a possible olmesartan side effect. Potassium is necessary for the proper functioning of your heart and muscles. But too much potassium in your blood can be dangerous. In severe cases, it can cause life-threatening abnormal heart rhythms.

High potassium doesn’t always cause symptoms, so your healthcare team may discover it during a routine checkup. If your potassium levels are higher than normal, they may adjust your dosage or switch you to a different medication.

If you develop symptoms such as severe muscle weakness or a fast or irregular heartbeat, call 911 or have someone take you to the nearest ER.

9. Kidney problems

ARBs such as olmesartan can have kidney-related benefits for certain people. But there are also situations where it can affect how well your kidneys filter your blood. This may be more likely to happen in people with heart failure. Taking olmesartan with nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen (Advil, Motrin), can also increase this risk.

Your healthcare team may periodically monitor your kidney function while you’re taking olmesartan. If there are signs of kidney damage, they may lower your dose or have you stop olmesartan. But you should tell them right away if you develop symptoms such as reduced urination, swelling in your ankles or legs, and fatigue.

When should you contact your prescriber about olmesartan side effects?

Dizziness is the most common olmesartan side effect, and it tends to get better as your body adjusts to the medication. But don’t hesitate to contact your healthcare team if any side effects are persistent, getting worse, or generally concern you.

While most olmesartan side effects are mild, some are more serious and require medical attention. These include severe diarrhea, a fast or irregular heartbeat, and swelling of the face, tongue, and throat. But if any symptoms you’re experiencing feel severe or life-threatening, go to the nearest ER.

Good to know: Some olmesartan side effects may be more likely if you’re taking interacting medications. Be sure to share your current medication list with your healthcare team to check for interactions in advance.

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Written by:

Alex Evans, PharmD, MBA

Alex Evans, PharmD, MBA, has been a pharmacist for 12 years. His first job was floating in a community chain pharmacy.

Edited by:

Alyssa Billingsley, PharmD

Alyssa Billingsley, PharmD, is the director of pharmacy content for GoodRx. She has over a decade of experience as a pharmacist and has worked in clinical, academic, and administrative roles.

Reviewed by:

Christina Aungst, PharmD

Christina Aungst, PharmD, is a pharmacy editor for GoodRx. She began writing for GoodRx Health in 2019, transitioning from freelance writer to editor in 2021.

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