Losartan: what it’s for and how to use it safely

If your doctor mentioned losartan, you probably want straight answers: what it does, what to watch for, and simple steps to stay safe. Losartan is an angiotensin II receptor blocker (ARB). Doctors use it mostly to lower blood pressure and to protect kidneys in people with type 2 diabetes. It’s often chosen when ACE inhibitors cause a cough or aren’t tolerated.

How losartan works and when it’s used

Losartan blocks a hormone that tightens blood vessels. That makes vessels relax, which lowers blood pressure and eases the heart’s workload. It’s commonly prescribed for: high blood pressure, protecting kidney function in diabetes with protein in the urine, and sometimes to help after heart problems. Typical starting doses vary (often 25–50 mg once daily), but don’t change your dose without talking to your prescriber.

Side effects, interactions, and safety tips

Most people tolerate losartan well, but watch for a few things. Common mild effects include dizziness (especially when standing up), tiredness, or stomach upset. A less common issue is skin rash — if you notice a rash after starting losartan, tell your doctor; one of our site posts covers losartan-induced rash in detail and when it needs urgent care.

Serious signs that need quick attention are swelling of the face or throat, trouble breathing, or fainting. These could mean a severe allergic reaction or a dangerous drop in blood pressure.

Drug interactions matter. Avoid taking potassium supplements or salt substitutes with extra potassium unless your clinician says it’s OK — losartan can raise potassium. NSAIDs like ibuprofen can blunt blood-pressure control or affect kidney function when combined with losartan. Combining losartan with ACE inhibitors or aliskiren is generally not recommended. Always tell your provider about all meds and supplements you take.

Labs and monitoring: your doctor may check kidney function and potassium a few weeks after starting or increasing the dose. If you have kidney disease or low blood pressure to begin with, monitoring is especially important.

Pregnancy warning: ARBs like losartan can harm a developing baby. If you’re pregnant or planning pregnancy, stop losartan and call your doctor right away.

Practical tips that help every day:

• Take it at the same time each day to build a habit.
• If you feel dizzy when standing, sit or lie down until it passes and mention it at your next visit.
• Keep a home blood-pressure log for a week before your next doctor visit — it gives real data, not guesses.
• Bring a complete meds list to appointments, including OTCs and supplements.

Questions about a rash, unusual symptoms, or starting/stopping losartan? Reach out to your prescriber. If you want more details, read our full article about losartan-induced rash and related posts on drug interactions and blood-pressure care on Top-Meds.org.