Benicar (Olmesartan) side effects: from common ones like dizziness and diarrhea to serious reactions. Know when to call your doctor.
Every medication comes with potential side effects, and Benicar (Olmesartan) is no exception. The good news is that most people tolerate it well, and serious side effects are uncommon. But knowing what to watch for — and when to contact your doctor — helps you stay safe while managing your blood pressure.
This guide covers the common and serious side effects of Benicar based on FDA labeling, who may be at higher risk, and practical tips for managing side effects if they occur.
Benicar is the brand name for Olmesartan Medoxomil, an angiotensin II receptor blocker (ARB) used to treat high blood pressure. It works by blocking a chemical called angiotensin II that tightens blood vessels, allowing your blood vessels to relax and your blood pressure to drop. For more details on how Benicar works, see our mechanism of action guide.
Benicar is available in 5 mg, 20 mg, and 40 mg tablets. The typical dose is 20 mg to 40 mg once daily.
These side effects affect a noticeable percentage of patients in clinical trials. Most are mild and often improve as your body adjusts to the medication over the first few weeks:
If any common side effect is bothering you or not improving after a few weeks, talk to your doctor. They may adjust your dose or suggest a different approach.
These are less common but require prompt medical attention:
This is a condition unique to Olmesartan among the ARB class. Symptoms include severe, chronic diarrhea with substantial weight loss, sometimes starting months or even years after beginning the medication. It mimics celiac disease but is caused by the drug, not gluten. If you develop ongoing diarrhea and unexplained weight loss while taking Benicar, contact your doctor immediately. The condition typically resolves after stopping the medication.
Benicar can raise potassium levels in your blood. Symptoms of dangerously high potassium include muscle weakness, slow or irregular heartbeat, and tingling or numbness. Your doctor should check your potassium levels with routine blood work, especially if you take potassium supplements or potassium-sparing diuretics.
ARBs like Benicar can affect kidney function, particularly in people who already have kidney disease, are dehydrated, or take NSAIDs. Signs include decreased urination, swelling in your legs or ankles, and unexplained fatigue. Regular lab work monitors for this.
If your blood pressure drops too low, you may feel very dizzy, lightheaded, or faint. This is more common in people who are dehydrated or on multiple blood pressure medications. If you experience severe dizziness or actually faint, seek medical attention.
Rarely, Benicar can cause sudden swelling of the face, lips, tongue, or throat. This can interfere with breathing and is a medical emergency. Call 911 or go to the emergency room immediately if this occurs.
In very rare cases, muscle breakdown can occur. Symptoms include severe muscle pain, weakness, and dark-colored urine. Seek immediate medical attention if you experience these symptoms.
Some groups need extra caution with Benicar:
Benicar carries an FDA boxed warning — the most serious type — for fetal toxicity. It is contraindicated during the second and third trimesters of pregnancy because it can cause injury and death to a developing fetus. If you become pregnant while taking Benicar, stop the medication and contact your doctor as soon as possible.
It's not known whether Olmesartan passes into breast milk. Benicar is generally not recommended while breastfeeding. Talk to your doctor about alternatives.
Benicar is FDA-approved for children aged 6 and older for hypertension. Dosing is weight-based and should be managed by a pediatric specialist.
No dose adjustment is typically needed, but older adults should have their kidney function monitored more closely since kidney function naturally declines with age.
Use Benicar with caution if you have kidney impairment — it can worsen kidney function. No dose adjustment is needed for mild to moderate liver impairment, but data is limited for severe liver disease.
Most Benicar side effects are manageable with simple strategies:
Always keep your follow-up appointments so your doctor can monitor your blood pressure, potassium levels, and kidney function. For more information on what Benicar is used for and how to take it, see our complete Benicar guide.
Contact your doctor if you experience:
Call 911 immediately if you have swelling of your face, lips, tongue, or throat, or difficulty breathing.
Benicar is an effective blood pressure medication that most people tolerate well. Common side effects like dizziness and diarrhea are usually mild and temporary. The most important thing to watch for is severe, persistent diarrhea — a side effect unique to Olmesartan — and signs of high potassium or kidney problems.
Don't stop taking Benicar without talking to your doctor, even if you experience side effects. Suddenly stopping blood pressure medication can cause a dangerous spike in blood pressure. Your doctor can help you manage side effects or switch to an alternative medication if needed.
Looking for Benicar at the best price? Check out our savings guide or use Medfinder to find it in stock near you.
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