Losartan

Losartan: How It Works, Potassium Checks & Why It Doesn't Cause a Dry Cough

Losartan is a sartan (AT1 receptor blocker) and lowers blood pressure by blocking the effect of angiotensin II, the messenger that drives pressure up. It is often used when an ACE inhibitor is not tolerated because of a dry cough, and it also protects the kidneys. One special feature: losartan slightly lowers uric acid, which can be an advantage for people with gout.

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Contents

  1. At a Glance: Technical Data Sheet
  2. How it works: what losartan does in your body
  3. Dosage: starting low and adjusting
  4. Taking it: timing, meals, a missed dose
  5. Side effects and what helps against them
  6. No dry cough: switching from an ACE inhibitor
  7. Interactions: NSAIDs, potassium, lithium
  8. Lab values: potassium and kidney function
  9. Losartan compared with other sartans
  10. Special situations: pregnancy, older age, kidneys
  11. Losartan experiences: what patients really ask
  12. FAQ: Common questions about losartan

1. At a Glance: Technical Data Sheet

PropertyDetails
Active substanceLosartan (as losartan potassium)
ATC codeC09CA01
Substance classAT1 receptor blocker (“sartan”, angiotensin II receptor antagonist)
Available formsFilm-coated tablets, usually 12.5 mg, 25 mg, 50 mg and 100 mg; also as a fixed combination with hydrochlorothiazide
Half-lifeLosartan itself around 2 hours, its active metabolite considerably longer — which is why one dose a day is usually enough
Maximum daily dose100 mg according to the Summary of Product Characteristics; your individual dose is set by your doctor
Onset of actionA first drop in blood pressure within hours, the full effect usually only after 3 to 6 weeks
Prescription statusPrescription-only in Germany
Special featureNo typical dry cough as seen with ACE inhibitors; also lowers uric acid slightly
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2. How it works: what losartan does in your body

Your body regulates blood pressure and salt balance through the so-called renin-angiotensin-aldosterone system. The central messenger in it is angiotensin II. It narrows the blood vessels and makes the kidneys hold on to sodium and water — both of which push blood pressure up.¹

Losartan blocks the docking site for this messenger, the AT1 receptor. The vessels stay wider, the kidneys excrete more sodium, blood pressure falls. Because losartan blocks the receptor rather than — like an ACE inhibitor — preventing angiotensin II from being formed, it acts at a later point in the same chain.

Three things follow directly from this mechanism:

  • Kidney protection: pressure inside the filtering units of the kidney drops and protein loss into the urine goes down. That is why sartans are preferred in chronic kidney disease and in type 2 diabetes with protein in the urine.
  • Potassium rises: less aldosterone means the kidneys excrete less potassium. This is the most important lab observation on losartan.
  • No bradykinin effect: ACE inhibitors let the messenger bradykinin build up, which triggers the familiar dry, tickly cough. Losartan does not do this — more on that in section 6.

3. Dosage: starting low and adjusting

The following describes what the Summary of Product Characteristics sets out as the usual approach. It is not a recommendation on how to take it — your dose is set by your doctor and adjusted according to blood pressure and lab values.

  • Starting dose: frequently 50 mg once daily; in older people, when fluid levels are low or when diuretics are being taken, treatment usually starts lower.
  • Increases: as a rule no earlier than after several weeks, because the full effect only shows by then.
  • Maximum dose: 100 mg daily according to the Summary of Product Characteristics.
  • Combination: if one substance is not enough, a calcium channel blocker such as amlodipine or a thiazide such as hydrochlorothiazide is usually added.
Patience is part of the treatment. Many people measure after three days, are disappointed and stop. But blood pressure falls slowly on losartan. How to measure properly at home is explained in the guide measuring blood pressure correctly.

4. Taking it: timing, meals, a missed dose

Losartan is uncomplicated in everyday life — the one thing that really matters is regularity.

  1. Pick a fixed time of day. Whether morning or evening is, according to current evidence, of secondary importance with losartan. What counts is that it happens at the same time every day.
  2. Meals make no difference. You can take the tablet with or without food, with a glass of water.
  3. Watch out for dizziness while the dose is being built up. Stand up slowly, especially in the first few days — blood pressure can drop more sharply for a short time.
  4. A missed dose: as a rule it is taken later the same day if it is still early enough; doubling up is not a solution. What applies in general is set out in the guide forgot your blood pressure medication.
  5. Do not pause on your own initiative. Even when the readings look good: good blood pressure is the result of the treatment, not the end of it.
Take care with diarrhoea, vomiting and heat. If you lose a lot of fluid, blood pressure can fall sharply on losartan and kidney function can suffer — particularly in combination with diuretics such as torasemide and with painkillers. Speak to your doctor in such phases instead of simply carrying on. Background in the guide medications and heat.

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5. Side effects and what helps against them

Losartan is considered comparatively well tolerated. Most complaints occur while the dose is being adjusted and then ease off.

More common and usually harmless

  • Dizziness and light-headedness — above all when standing up quickly. Getting up slowly and drinking enough usually helps.
  • Fatigue — common in the first weeks, often receding afterwards.
  • Headache — usually temporary.

Rarer, but important to know

  • Potassium too high (hyperkalaemia): often causes no symptoms at first, but can trigger heart rhythm problems. That is why it is monitored (section 8).
  • Worsening kidney values: a slight rise in creatinine after treatment starts is known and usually acceptable; a sharp rise is a warning sign.
  • Muscle complaints and calf cramps — more common when a diuretic is taken as well.
Seek medical help immediately. Sudden swelling of the lips, tongue, face or throat, or difficulty breathing or swallowing, raises the suspicion of angioedema — that is an emergency, call 112 (the emergency number in Germany). Angioedema is very rare on sartans, but it does happen, even after long-term use. Report unusual reactions afterwards; see medication side effects.

6. No dry cough: switching from an ACE inhibitor

The most common reason someone is given losartan is a persistent dry cough on an ACE inhibitor such as ramipril, enalapril or lisinopril. This cough is not a cold: it is dry, tickly, often worse at night, and it does not go away on its own as long as the medication is being taken.

The cause is the messenger bradykinin, which builds up on ACE inhibitors and irritates the cough receptors. Sartans such as losartan act at a different point and, according to current evidence, do not trigger this effect — which is why switching is the established solution.¹,²

What you should know about the switch. The cough can linger for days or a few weeks after the ACE inhibitor is stopped — that does not mean the switch has failed. The blood-pressure-lowering effect is comparable between the two groups, as are the requirements for potassium and kidney monitoring. The two groups are not combined with each other.

A second, often overlooked plus point: losartan lowers uric acid slightly because it promotes its excretion through the kidneys. For people with gout that can be an argument for this particular sartan — but it does not replace specific treatment with allopurinol.

7. Interactions: NSAIDs, potassium, lithium

Almost all of the relevant interactions of losartan come down to two questions: what happens to potassium, and what happens to blood flow through the kidneys?

CombinationConsequenceWhat to do
NSAIDs (e.g. ibuprofen, diclofenac)The blood-pressure-lowering effect is weakened, kidney function can sufferOnly short term and after checking with your doctor; discuss alternatives such as paracetamol
NSAIDs plus a diuretic at the same timeClearly increased risk of acute kidney failure (the “triple whammy”)Have this combination checked specifically by your doctor or pharmacist
Potassium-sparing diuretics such as spironolactone, potassium supplements, salt substitutesPotassium can rise to dangerous levelsOnly with monitoring of the potassium value; avoid potassium-based salt substitutes
LithiumLithium levels can riseClose monitoring of blood levels
An ACE inhibitor or aliskiren in additionMore side effects without additional benefitDual blockade is generally avoided
AlcoholStronger fall in blood pressure, more dizzinessBe cautious, especially while the dose is being adjusted
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The practically most important point is the first one: NSAID painkillers are available without a prescription and are often not perceived as “real” medicines. Yet they are exactly what weakens the effect of losartan and, combined with diuretics, puts a strain on the kidneys. Check such combinations in the guide to drug interactions or directly in the interaction check of the brite app. On the subject of alcohol, the guide medications and alcohol is worth reading.

8. Lab values: potassium and kidney function

Two values accompany every sartan therapy: potassium and creatinine or eGFR as a measure of kidney function.

  • Before treatment starts: establish baseline values.
  • After starting and after every dose increase: a check, as a rule within the first weeks.
  • During ongoing treatment: checks depending on kidney function and other medication, but regularly at the very least.
  • Additionally when there is a reason: with diarrhoea, vomiting, fever, a heatwave or new painkiller treatment.

A slight rise in creatinine after treatment starts is known and does not automatically argue against the treatment — it reflects the changed pressure distribution inside the kidney. How to make sense of results is explained in the guide understanding blood values; what generally applies with impaired kidney or liver function is covered under medications with kidney and liver disease.

Potassium-rich food is not forbidden. You do not have to cut out bananas, dried fruit and nuts on losartan. What does deserve attention are potassium-based salt substitutes and food supplements containing potassium — they deliver large amounts unnoticed. See also supplements and medications.

9. Losartan compared with other sartans

All sartans work through the same mechanism. The differences lie mainly in how long they act and in a few practical details.

Active substanceSpecial featurePractically relevant
LosartanShortest duration of action in the group, lowers uric acid slightlyAn advantage with gout; with very high readings the 24-hour cover is sometimes not enough
CandesartanLong duration of action, fine dose stepsFrequently used in high blood pressure and heart failure
ValsartanBroad evidence base after a heart attack and in heart failureAlso available in combination with sacubitril
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Which sartan fits in an individual case depends on accompanying conditions such as heart failure or high blood pressure, on kidney values and on how well it is tolerated. Switching within the group is possible, but it is not a matter for self-medication.

10. Special situations: pregnancy, older age, kidneys

Not in pregnancy. Sartans are not suitable in pregnancy or when trying to conceive without reliable contraception — they can seriously harm the unborn child, particularly from the second trimester onwards. If you are pregnant or would like to become pregnant, talk to your doctor promptly about switching, but do not stop anything on your own. Orientation is offered by medications during pregnancy.

In older age treatment usually starts lower, because drops in blood pressure increase the risk of falls. When several medicines are taken at once, it is worth looking at polypharmacy and medications in old age.

With impaired kidney function losartan is not forbidden — on the contrary, it is frequently used precisely then. It does, however, require closer monitoring of potassium and eGFR, and it is not suitable if both renal arteries are narrowed.

11. Losartan experiences: what patients really ask

“I don't feel anything at all — is it even working?”

High blood pressure usually does not hurt, and so treating it feels like nothing at all. That is normal and no sign that the medicine is not working. The only reliable evidence is measured readings over several weeks — ideally always at the same time of day and at rest. That is exactly why a record you can show at your appointment is worth more than the feeling of individual days.

“Can I stop losartan if my readings are good?”

Good readings are the result of the treatment. If it ends, blood pressure usually rises again. There are situations in which the dose can be reduced — after significant weight loss or a change in lifestyle habits, for example. That decision belongs to your doctor, not to a gut feeling. Background in the guide stopping medications and practical approaches under lowering blood pressure naturally.

“I forgot my tablet on holiday — what now?”

A single missed dose is usually uncritical with losartan. It becomes a problem when one day turns into a week because the pack did not travel with you. Plan the quantity generously, keep it in your hand luggage and set yourself a reminder. More on this under medications when travelling.

“My GP switched me to a different product — is it the same thing?”

Switches between manufacturers of the same active substance are common, in Germany often because of rebate contracts with health insurers. The active substance and the dose stay the same; the appearance and the name change. The only important thing is that you do not accidentally take both packs in parallel. How to make sense of this is explained in generics vs. brand-name medicines.

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FAQ: Common questions about losartan

A first drop in blood pressure sets in within hours, but according to the Summary of Product Characteristics the full effect usually only shows after three to six weeks. That is why the dose is normally not adjusted earlier. Judge the effect from readings taken over several weeks, not from individual days.
According to current evidence the timing is of secondary importance; what matters is regularity. Some doctors recommend taking it in the evening if blood pressure stays too high at night. Follow the instructions from your own practice and do not keep changing the time.
ACE inhibitors let the messenger bradykinin build up, and it irritates the cough receptors. Losartan instead blocks the receptor for angiotensin II and does not affect bradykinin. That is why switching to a sartan is the usual solution for ACE inhibitor cough.
Occasionally and briefly this is acceptable for many people, but not on a permanent basis. NSAIDs weaken the blood-pressure-lowering effect and can put a strain on kidney function, particularly together with diuretics. Discuss painkillers with your doctor or pharmacist instead of simply adding them.
As a rule no. Normal amounts of fruit, vegetables and nuts are not a problem. Caution is needed with potassium-based salt substitutes and potassium supplements, and when your kidney function is impaired or you also take potassium-sparing diuretics.
Alcohol lowers blood pressure itself and intensifies dizziness and light-headedness. Being cautious makes sense above all while the dose is being adjusted. Larger amounts also raise blood pressure in the long run and therefore work against the treatment.
With heavy fluid loss blood pressure can drop sharply and the kidneys can come under strain. Some practices agree rules in advance for when blood pressure medicines and diuretics should be paused. Ask about this, and do not decide it spontaneously on your own.
Losartan promotes the excretion of uric acid and thereby lowers it slightly, unlike thiazide diuretics, which can raise it. With gout that can be an argument, but it does not replace targeted uric-acid treatment. The choice is made by your doctor.

Sources

  1. Summary of Product Characteristics (SmPC) for losartan potassium, current version, available via the medicines information system of the licensing authorities (Germany). pharmnet-bund.de
  2. NICE guideline NG136: Hypertension in adults — diagnosis and management. nice.org.uk
  3. NHS: Losartan — how and when to take it, side effects. Accessed 2026. nhs.uk
  4. MSD Manual, Consumer Version: Drug treatment of high blood pressure. Accessed 2026. msdmanuals.com
  5. Embryotox, Charité — pharmacovigilance and advisory centre (Germany): sartans in pregnancy. Accessed 2026. embryotox.de

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Medical disclaimer: This article is for general information and does not replace medical advice, diagnosis or treatment. Never stop losartan on your own initiative and do not change the dose yourself — not even when your blood pressure readings are good. If you notice swelling of the face or throat, shortness of breath, or if you suspect you are pregnant, contact a doctor promptly or, in an emergency, call 112 (the emergency number in Germany). The choice of medicine and the dose are always determined individually by your doctor. Last updated: August 2026.