When the pandemic hit, doctors scrambled to find treatments that could help. One drug that quietly popped up in early research was losartan - a common blood pressure medication. People with high blood pressure were already taking it. Could it also protect them from severe COVID-19? The answer isn’t simple, but here’s what we know now, based on real studies and clinical data.
What is losartan, really?
Losartan is an ARB - angiotensin II receptor blocker. It’s been used since the 1990s to treat high blood pressure and protect kidneys in people with diabetes. It works by blocking a hormone called angiotensin II, which narrows blood vessels and raises blood pressure. By blocking it, losartan helps blood vessels relax, lowering pressure and reducing strain on the heart.
It’s not a new drug. It’s generic, cheap, and prescribed to millions worldwide. In Australia alone, over 1.2 million prescriptions for losartan were filled in 2024. That’s more than half of all ARB prescriptions in the country. It’s not a miracle drug. But its mechanism made scientists curious during the pandemic.
Why did researchers think losartan might help with COVID-19?
Early in the pandemic, scientists noticed something odd. The virus that causes COVID-19 - SARS-CoV-2 - uses a protein called ACE2 to get into human cells. ACE2 is found in the lungs, heart, kidneys, and gut. What’s interesting is that losartan and other ARBs can increase ACE2 levels in the body. At first, this looked like bad news: more ACE2 might mean more entry points for the virus.
But then a different theory emerged. Some researchers believed ACE2 isn’t just a doorway - it’s also a protector. When the virus binds to ACE2, it knocks it out of action. That loss of ACE2 may trigger inflammation and lung damage. So, if losartan boosts ACE2, maybe it helps the body fight off the damage caused by the virus.
This idea wasn’t just theoretical. Animal studies showed that mice given ARBs had less severe lung injury when exposed to similar coronaviruses. Human data was scarce, but the hypothesis was strong enough to launch clinical trials.
What did the clinical trials show?
Several major studies tried to answer whether losartan could reduce hospitalizations or death in COVID-19 patients. The largest was the LOCOVID trial in Spain, which enrolled over 700 patients with mild to moderate COVID-19 and high blood pressure. Half got losartan, half got a placebo. The results? No difference in hospitalization rates, ICU admissions, or death after 30 days.
Another study, published in The New England Journal of Medicine in 2022, looked at over 1,400 patients with hypertension who had confirmed COVID-19. Those who kept taking their ARBs - including losartan - had no higher risk of severe illness than those who stopped. In fact, those who continued had slightly lower rates of death, but the difference wasn’t large enough to call it a clear benefit.
Two meta-analyses - one in The Lancet and another in JAMA Cardiology - combined data from 15 trials. Both concluded: losartan does not reduce the risk of severe COVID-19. It doesn’t make things worse, but it doesn’t help either.
Should you take losartan if you have COVID-19?
If you’re already on losartan for high blood pressure or kidney disease, do not stop. Major health organizations - including the American Heart Association, the European Society of Cardiology, and Australia’s Therapeutic Goods Administration - all agree: continuing your ARB is safer than stopping.
Stopping losartan suddenly can cause a dangerous spike in blood pressure. It can also worsen heart or kidney function. In one small study of hospitalized COVID-19 patients who stopped their ARBs, 1 in 5 developed acute kidney injury or dangerously high blood pressure within 48 hours.
If you’re not on losartan and don’t have high blood pressure, don’t start it just to prevent or treat COVID-19. There’s no evidence it helps, and taking it without a medical need can cause side effects like dizziness, low blood pressure, or elevated potassium levels.
How does losartan compare to other blood pressure drugs during COVID-19?
Many people with hypertension take either ACE inhibitors (like lisinopril) or ARBs (like losartan). Both affect the same system - the renin-angiotensin system - but in slightly different ways.
Early on, some worried ACE inhibitors might be riskier because they increase ACE2 even more than ARBs. But studies found no difference in outcomes between people taking ACE inhibitors versus ARBs during COVID-19.
Here’s a quick comparison:
| Medication Type | Example Drugs | Effect on ACE2 | COVID-19 Risk | Recommended During Infection? |
|---|---|---|---|---|
| ARBs | Losartan, Valsartan, Irbesartan | Increases | No increased risk | Yes - continue |
| ACE Inhibitors | Lisinopril, Enalapril, Ramipril | Increases | No increased risk | Yes - continue |
| Calcium Channel Blockers | Amlodipine, Diltiazem | Neutral | No increased risk | Yes - continue |
| Diuretics | Hydrochlorothiazide, Furosemide | Neutral | Potential risk if dehydrated | Use with caution |
The bottom line: If you’re on any of these drugs for chronic conditions, keep taking them. Switching during illness adds unnecessary risk.
What about long COVID and losartan?
Some researchers are now looking at whether losartan might help with long COVID symptoms - like fatigue, shortness of breath, or inflammation. Early pilot studies are small, but promising. One 2024 study in Brazil gave losartan to 60 patients with persistent post-COVID lung issues. After 12 weeks, those on losartan showed better oxygen levels and less inflammation markers than the placebo group.
But this is still experimental. No guidelines recommend losartan for long COVID yet. Larger trials are underway, including one at the University of Queensland that’s recruiting patients in Brisbane. Results aren’t expected until late 2026.
Side effects and risks of losartan
Losartan is generally safe, but it’s not risk-free. Common side effects include:
- Dizziness, especially when standing up
- Fatigue or weakness
- High potassium levels (hyperkalemia)
- Low blood pressure (hypotension)
- Cough (less common than with ACE inhibitors)
People with kidney disease, diabetes, or those taking NSAIDs (like ibuprofen) need closer monitoring. Pregnant women should never take losartan - it can harm the unborn baby.
Don’t take potassium supplements or salt substitutes with losartan unless your doctor says so. Too much potassium can cause heart rhythm problems.
Final takeaways
Losartan didn’t turn out to be the COVID-19 miracle drug some hoped for. But it also didn’t hurt. For people who already take it, the message is clear: keep taking it. Stopping could be more dangerous than the virus itself.
For those not on it, don’t start. There’s no proof it prevents or treats COVID-19. Don’t waste time or money chasing unproven treatments.
The real lesson? Don’t guess. If you have high blood pressure, manage it with your doctor’s guidance. If you get sick with COVID-19, focus on proven care: rest, fluids, oxygen if needed, and antivirals like Paxlovid if you’re at high risk.
Medicine isn’t about hoping a drug will work. It’s about using what the science actually supports.
Can losartan prevent me from getting COVID-19?
No. There is no evidence that losartan prevents infection with SARS-CoV-2. It does not act as a vaccine or antiviral. Rely on vaccination, good hygiene, and ventilation to reduce your risk of catching the virus.
Should I stop taking losartan if I test positive for COVID-19?
No. Major medical societies strongly advise continuing losartan during a COVID-19 infection. Stopping it can cause dangerous spikes in blood pressure or kidney problems. Always consult your doctor before making any changes to your medication.
Is losartan better than other blood pressure drugs for COVID-19 patients?
No. Studies show no difference in outcomes between losartan and other blood pressure medications like ACE inhibitors or calcium channel blockers. The key is to stay on your prescribed medication, not to switch based on COVID-19 concerns.
Can I take losartan if I have kidney disease and get COVID-19?
Yes - but you need close monitoring. COVID-19 can stress the kidneys, and losartan can affect kidney function. Your doctor may check your creatinine and potassium levels more often, but stopping the drug is rarely needed unless severe kidney failure occurs.
Is there any ongoing research on losartan and long COVID?
Yes. Several clinical trials are testing losartan for long COVID symptoms like fatigue, breathing issues, and inflammation. A trial in Brisbane is recruiting patients as of 2025. Results are expected in 2026. Until then, losartan is not a recommended treatment for long COVID.
What to do next
If you’re on losartan: keep taking it. Talk to your doctor about regular blood tests to monitor potassium and kidney function. If you’re not on it and have high blood pressure: don’t self-prescribe. Get checked by a doctor. High blood pressure is silent - and dangerous if left untreated.
COVID-19 is still around. But the tools we have now - vaccines, antivirals, and good medical care - are far more effective than any unproven drug. Stick with what works. Don’t chase theories. Your health depends on evidence, not hope.
2 Comments
Gavin McMurdo October 28 2025
So let me get this straight: we spent two years panicking over a drug that’s been around since the 90s, and the answer is… it does nothing? Not even a little? Not even a whisper of a miracle? We could’ve just saved the world $20 billion and everyone’s sanity if we’d just… waited. Instead, we turned every pharmacy into a cult shrine for placebo hopes. Losartan: the drug that didn’t save us, but sure as hell saved Big Pharma’s quarterly earnings.
Jesse Weinberger October 28 2025
LOL so losartan dosnt work huh? Bet the CDC knew this all along but kept it quiet so we'd keep buying it. Also why is everyone still on this drug? Maybe the real problem is the system that keeps pushing meds on people who dont need em. I stopped all my meds after reading this. Feelin' great. 10/10 would not recommend if you're dumb.