ARB stands for angiotensin II receptor blocker, a class of prescription medication primarily used to lower blood pressure. ARBs are one of four drug classes recommended as first-line treatment for high blood pressure in adults, according to the 2025 guidelines from the American Heart Association and American College of Cardiology. They work by blocking a hormone that tightens blood vessels, allowing blood to flow more easily and reducing the workload on your heart.
How ARBs Work
Your body produces a hormone called angiotensin II as part of a system that regulates blood pressure and fluid balance. This hormone causes blood vessels to constrict and signals your body to retain sodium and water, both of which raise blood pressure. ARBs block the receptor that angiotensin II binds to on blood vessel walls, preventing it from doing its job. The result: your blood vessels relax, your blood pressure drops, and your heart doesn’t have to pump as hard.
This mechanism also explains why ARBs protect the kidneys. In people with kidney disease, especially from diabetes, ARBs dilate the tiny blood vessels leaving the kidney’s filtering units. That reduces pressure inside those filters and slows damage over time. Research shows ARBs reduce the amount of protein leaking into urine (an early sign of kidney damage) independently of their blood pressure effects.
Common ARB Medications
There are eight ARBs currently available:
- Losartan, the most widely prescribed
- Valsartan
- Irbesartan
- Candesartan
- Olmesartan
- Telmisartan
- Azilsartan
- Eprosartan
All of them work through the same basic mechanism, but they differ in how long they stay active in your body and how potent they are at a given dose. Most are taken once daily. Valsartan, for example, is typically started at 80 mg once daily for high blood pressure, with doses ranging up to 320 mg. For heart failure, it’s usually taken twice daily at lower doses. Your prescriber picks a specific ARB based on your condition, other medications, and how your body responds.
What ARBs Are Prescribed For
High blood pressure is the most common reason people take an ARB, but it’s not the only one. ARBs are also prescribed for heart failure, chronic kidney disease, and kidney damage caused by diabetes. The 2025 AHA/ACC guidelines specifically recommend an ARB (or an ACE inhibitor) as the preferred starting medication for people with high blood pressure who also have chronic kidney disease with significant protein in their urine, because of long-term kidney and cardiovascular benefits.
ARBs vs. ACE Inhibitors
ACE inhibitors (like lisinopril and ramipril) target the same blood pressure system but at a different point. They prevent angiotensin II from being produced in the first place, while ARBs block it after it’s made. Both lower blood pressure effectively, and you wouldn’t take both at the same time.
The biggest practical difference is cough. ACE inhibitors cause a persistent dry cough in roughly 4% to 35% of people who take them. ACE inhibitors carry about 3.2 times the risk of cough compared to ARBs. In a large trial of over 25,000 participants, 4.2% of people on the ACE inhibitor ramipril stopped taking it because of cough, compared to just 1.1% on the ARB telmisartan. This is the main reason doctors switch someone from an ACE inhibitor to an ARB: same blood pressure benefit, far less chance of that nagging cough.
Side Effects
ARBs are generally well tolerated, which is one reason they’re a first-line option. The most common side effects include dizziness (from blood pressure dropping too low), elevated potassium levels, and changes in kidney function. Dizziness is most likely when you first start the medication or when the dose increases, and it often improves as your body adjusts.
Elevated potassium deserves attention because it can affect heart rhythm if it gets too high. The risk goes up if you already have kidney problems or take other medications that raise potassium, including certain diuretics, anti-inflammatory painkillers like ibuprofen, or potassium supplements. Routine blood tests to check your potassium and kidney function are standard when you’re on an ARB, especially early on.
Pregnancy Warning
ARBs carry an FDA black box warning, the most serious category, for use during pregnancy. Taking an ARB during the second or third trimester reduces kidney function in the developing fetus and can cause serious harm or death. If you become pregnant while taking an ARB, it should be stopped as soon as possible. This warning applies to the entire ARB class, not just specific drugs within it.
The Nitrosamine Recall Issue
Starting in 2018, several ARBs, particularly valsartan and losartan, were recalled after manufacturers discovered contamination with nitrosamines, chemicals that may increase cancer risk with long-term exposure above certain levels. This understandably worried many patients.
The FDA has since set internationally recognized acceptable daily intake limits for nitrosamines. At or below those limits, taking a contaminated drug every day for 70 years would not be expected to increase cancer risk. Manufacturers are now required to test for these impurities and recall any batches that exceed safe levels. As of 2024, the FDA issued updated guidance tightening requirements for how drug makers detect and prevent nitrosamine contamination. If you’re currently taking an ARB, your pharmacy is dispensing products that meet these safety standards.