Losartan is not a beta blocker. It belongs to a completely different class of medication called angiotensin receptor blockers, commonly known as ARBs. Both drug classes lower blood pressure, but they work through unrelated mechanisms in the body, produce different side effects, and are prescribed in different clinical situations.
How Losartan Actually Works
Losartan lowers blood pressure by blocking a hormone called angiotensin II from binding to receptors on your blood vessels. Angiotensin II normally causes blood vessels to tighten and narrow, which raises blood pressure. By blocking this signal at what’s known as the AT1 receptor, losartan allows blood vessels to relax and widen. It’s extremely selective for this one receptor type, binding to it over 10,000 times more strongly than to related receptors elsewhere in the body.
The FDA has approved losartan for treating high blood pressure and for protecting the kidneys in people with type 2 diabetes who have kidney disease (diabetic nephropathy). It’s also used to reduce stroke risk in certain patients with an enlarged heart.
How Beta Blockers Work Differently
Beta blockers target an entirely different system. They block receptors that respond to adrenaline (epinephrine) and norepinephrine, the “fight or flight” hormones. When these stress hormones are blocked, the heart beats more slowly and with less force. This is the hallmark effect of beta blockers: they directly slow your heart rate and reduce how hard your heart pumps with each beat.
Losartan does not do this. It has no direct effect on adrenaline receptors and does not meaningfully slow the heart. One study in patients with heart failure found that losartan lowered heart rate by roughly 5 to 8 beats per minute after 12 weeks, a modest and indirect change. Beta blockers, by contrast, produce a much larger and more immediate reduction in heart rate because slowing the heart is their primary job.
Why the Confusion Happens
People often mix up these two drug classes because both are prescribed for high blood pressure and both have names that end in similar-sounding suffixes. A quick way to tell them apart: generic beta blocker names almost always end in “-olol” (metoprolol, atenolol, propranolol, carvedilol), while ARBs like losartan end in “-sartan” (valsartan, irbesartan, candesartan). If your medication ends in “-sartan,” it’s an ARB, not a beta blocker.
Different Roles in Blood Pressure Treatment
Current guidelines from the American Heart Association and American College of Cardiology, updated in 2025, list ARBs like losartan as one of four first-line classes for treating high blood pressure. The other three first-line options are thiazide diuretics, calcium channel blockers, and ACE inhibitors. These four classes have the strongest evidence for lowering blood pressure effectively, preventing cardiovascular events, and being well tolerated.
Beta blockers are notably absent from that first-line list. The guidelines found beta blockers less effective than those four classes at preventing strokes and noted their less favorable side effect profile. Beta blockers are now reserved for people who have a specific reason to take them, such as heart failure, coronary heart disease, or certain heart rhythm problems. If your only diagnosis is high blood pressure without those conditions, a beta blocker is typically not the first choice.
Side Effects Compared
Because they work on different systems, losartan and beta blockers cause different side effects. Beta blockers are well known for causing fatigue, cold hands and feet, weight gain, and sometimes depression or sexual side effects. These stem from the heart beating more slowly and from blocking adrenaline’s effects throughout the body.
Losartan’s side effect profile looks different. The most commonly reported issues include dizziness, tiredness, and upper respiratory symptoms. A more specific concern with all ARBs is elevated potassium levels in the blood, so your doctor will typically monitor your potassium through routine blood work. Losartan should not be taken during pregnancy, as it can harm a developing baby.
One practical difference many people notice: because beta blockers directly suppress heart rate, they can make exercise feel harder. You may struggle to get your heart rate up during a workout and feel more easily winded. Losartan doesn’t blunt your exercise response in this way, which matters if you’re physically active.
Can You Take Both Together?
Yes. Doctors frequently prescribe an ARB and a beta blocker together, particularly for people with heart failure. In fact, most heart failure patients take both classes simultaneously. They complement each other because they lower blood pressure and protect the heart through completely independent pathways. Taking losartan doesn’t duplicate what a beta blocker does, so there’s a clear rationale for combining them when the clinical situation calls for it.
If you’re currently taking losartan and wondering whether you also need a beta blocker, or vice versa, the answer depends on your specific conditions. Someone with high blood pressure alone may do well on losartan by itself. Someone with high blood pressure plus a history of heart attack may benefit from adding a beta blocker to the regimen.