Myths About Losartan
Losartan is one of the most frequently dispensed blood pressure tablets in England. Its popularity has brought a crop of half-truths: that it causes cancer, that it is a secret muscle-building agent, that it can be stopped at will. Our editors examined the most persistent myths against the published evidence and official product information.
A quick reminder of what losartan does
Losartan belongs to the angiotensin II receptor blockers, often called ARBs or "sartans". It blocks the AT1 receptor, preventing angiotensin II from constricting blood vessels and stimulating aldosterone release. The result is lower blood pressure and reduced strain on the heart and kidneys.
In the UK it is prescription-only and is used for hypertension, for protecting the kidneys in type 2 diabetes with proteinuria, and in some patients with heart failure who cannot tolerate ACE inhibitors. NICE guideline NG136 places ARBs alongside ACE inhibitors as first-step options for certain patient groups.
Its major outcome trials, notably LIFE and RENAAL, showed reductions in stroke and in progression of diabetic kidney disease respectively. That solid evidence base sits uncomfortably next to some of the stories circulating online.
Myths matter because they change behaviour. People stop medicines out of fear, or start them without supervision in the hope of benefits that have not been demonstrated. Both can lead to harm.
Myth: "losartan causes cancer"
This fear has two separate origins. The first was a 2010 meta-analysis by Sipahi and colleagues that suggested a modest increase in new cancer diagnoses among people taking ARBs. It caused considerable alarm at the time.
A larger analysis by the ARB Trialists Collaboration, published in 2011 and including individual data from around 139,000 participants in 15 trials, found no increase in cancer risk with ARBs, losartan included. Regulators in Europe and the United States reviewed the issue and reached similar conclusions.
The second origin was the 2018–2019 discovery of nitrosamine impurities in some batches of sartan medicines from certain manufacturers. These impurities are probable carcinogens at long-term high exposure. Affected batches were recalled, and manufacturers changed their processes under regulatory supervision.
The recall concerned manufacturing contamination, not the losartan molecule itself. The MHRA advised patients not to stop their medicines but to speak to a pharmacist, because the risk of uncontrolled blood pressure was considered greater than the theoretical risk from impurities.
Myth: "losartan builds muscle and heals injuries"
This idea circulates in bodybuilding forums. It stems from laboratory work: Cohn and colleagues showed in mouse models that blocking AT1 receptors reduced TGF-beta signalling and improved muscle regeneration, and Burks and colleagues reported that losartan protected against disuse atrophy in ageing mice.
These were important experiments, but mouse models of muscular dystrophy and sarcopenia are a long way from a healthy young adult lifting weights. No controlled human study has shown that losartan increases muscle mass or strength in athletes or speeds healing of everyday sports injuries.
Using a blood pressure drug without a medical reason has real risks: dizziness and fainting during training, high potassium levels and kidney problems, especially when combined with dehydration or NSAIDs. These risks are not offset by any proven benefit.
| Myth | What the evidence shows |
|---|---|
| Causes cancer | Large pooled analysis found no increased risk; past recalls were due to impurities |
| Builds muscle in athletes | Only animal data; no human trials showing gains |
| Safe in pregnancy | Contraindicated in second and third trimesters; avoid when planning pregnancy |
| Can be stopped when BP is normal | BP usually normal because of the drug; stopping should be supervised |
| Any painkiller is fine with it | Regular NSAIDs can reduce its effect and harm kidneys |
Myths about safety in everyday life
"It's just a blood pressure pill, so it's safe in pregnancy." This is dangerous. Drugs acting on the renin–angiotensin system can damage the developing kidneys and skull of the fetus, particularly in later pregnancy. Women planning pregnancy should discuss switching medication in advance.
"Bananas and salt substitutes don't matter." Losartan can raise potassium levels, and salt substitutes are often potassium-based. Combined with potassium supplements or potassium-sparing diuretics, levels can rise dangerously. Normal dietary fruit is generally fine.
"Ibuprofen is harmless." Regular NSAIDs combined with an ARB and a diuretic, sometimes called the "triple whammy", increase the risk of acute kidney injury. Occasional use may be acceptable, but regular use should be discussed with a pharmacist.
"Exercise is risky on losartan." In fact regular activity is part of blood pressure management. Sensible precautions include staying hydrated, rising slowly after floor exercises and paying attention to dizziness, particularly in hot conditions or during illness with vomiting or diarrhoea.
Myths about how to take it
"Once my blood pressure is normal, I can stop." Normal readings usually mean the drug is working. Hypertension is generally a long-term condition, and stopping can allow pressure to climb again. Any change should be agreed with the prescriber.
"Losartan works instantly." The full blood pressure-lowering effect develops over several weeks. Judging the medicine after a few days is premature.
A few other common misunderstandings are worth clearing up:
- losartan does not need to be taken with food; consistency of timing matters more;
- it is not a diuretic, although it is often combined with one in a single tablet;
- it is not on the WADA Prohibited List, though combined products containing diuretics are prohibited in sport;
- blood tests for kidney function and potassium are routine after starting or changing the dose.
The last point is particularly relevant to competitive athletes: a combination tablet containing hydrochlorothiazide falls under the diuretic class of prohibited substances, and a therapeutic use exemption may be needed.
Conclusions of the editorial team
Losartan is a well-studied medicine with clear benefits for blood pressure, stroke and diabetic kidney disease. The cancer scare was not supported by large pooled analyses, and impurity recalls were a manufacturing problem that has been addressed.
Claims that it builds muscle or heals injuries in healthy people rest on animal research only and do not justify self-medication.
The real risks are practical: pregnancy, high potassium, dehydration and NSAID combinations. You may also find useful our articles on what the losartan clinical trials show, on atorvastatin research, and on blood pressure management for strength athletes.
References
- Dahlöf B, Devereux RB, Kjeldsen SE, et al. Cardiovascular morbidity and mortality in the Losartan Intervention For Endpoint reduction in hypertension study (LIFE): a randomised trial against atenolol. Lancet. 2002;359(9311):995–1003.
- Brenner BM, Cooper ME, de Zeeuw D, et al. Effects of losartan on renal and cardiovascular outcomes in patients with type 2 diabetes and nephropathy. N Engl J Med. 2001;345(12):861–869.
- Sipahi I, Debanne SM, Rowland DY, et al. Angiotensin-receptor blockade and risk of cancer: meta-analysis of randomised controlled trials. Lancet Oncol. 2010;11(7):627–636.
- ARB Trialists Collaboration. Effects of telmisartan, irbesartan, valsartan, candesartan, and losartan on cancers in 15 trials enrolling 138,769 individuals. J Hypertens. 2011;29(4):623–635.
- Cohn RD, van Erp C, Habashi JP, et al. Angiotensin II type 1 receptor blockade attenuates TGF-beta-induced failure of muscle regeneration in multiple myopathic states. Nat Med. 2007;13(2):204–210.
- Burks TN, Andres-Mateos E, Marx R, et al. Losartan restores skeletal muscle remodeling and protects against disuse atrophy in sarcopenia. Sci Transl Med. 2011;3(82):82ra37.
- National Institute for Health and Care Excellence. Hypertension in adults: diagnosis and management. NICE guideline NG136. London: NICE; 2019.
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