Losartan, an inexpensive oral prescription blood pressure medication, blocks a hormone that narrows blood vessels and retains salt. Its strongest evidence covers reliable blood pressure lowering and slower kidney decline in diabetic or protein-leaking kidney disease; moderate evidence links it to fewer strokes and less new diabetes. The longevity case rests mainly on animal studies. Main risks are high blood potassium, low blood pressure, and harm to a developing baby. (Full Review)

Protocol

Hypertension (product label)

50 mg once daily, up to 100 mg

Start 25 mg with possible fluid loss (volume depletion) or liver impairment

Single versus split dose

50 mg twice daily

Lowered 24-hour pressure more than 50 mg once daily, similar to 100 mg once daily; may help if evening readings rise

Time of day

Consistent timing

Evening vs morning dosing of usual blood pressure medications made no difference to cardiovascular events

Time to effect

Blood pressure

Within 1 week

Substantially present within one week; maximal effect at 3–6 weeks in some studies

Kidney protection

Years

Kidney outcome benefits emerged over years

Cardiovascular outcomes

Years

Cardiovascular outcome benefits emerged over years

Benefits

High: Blood pressure reduction; slower kidney disease progression

Medium: Fewer strokes than atenolol-based treatment; greater regression of thickened heart muscle; lower risk of new-onset diabetes; lower risk of atrial fibrillation (irregular heart rhythm); fewer heart failure hospitalizations; slower enlargement of the aortic root (main artery's base) in Marfan syndrome; lower uric acid and gout risk

Low: Longer lifespan; dementia prevention; muscle preservation and mobility in older adults; pancreatic cancer treatment add-on

Speculative: Protection of mitochondrial (cellular energy) function with aging; liver enzyme improvement in fatty liver disease

Contraindications

Pregnancy at any stage (boxed warning)

People with diabetes who take aliskiren; aliskiren with kidney filtering capacity (GFR) below 60 mL/min

Combined use with ACE inhibitors (lisinopril, enalapril, ramipril)

Hypersensitivity to any component of the product

Breastfeeding (unless the importance of the drug outweighs nursing)

Severe liver impairment (not studied)

Children under 6 years, or children with kidney filtering capacity (GFR) below 30 mL/min/1.73 m² (not recommended)

Prior angioedema during angiotensin receptor blocker use

Key Interactions

Potassium-sparing diuretics and aldosterone blockers (spironolactone, eplerenone, amiloride, triamterene), trimethoprim-sulfamethoxazole (co-trimoxazole), potassium supplements, potassium-containing salt substitutes (potassium chloride): Caution, high blood potassium

NSAIDs including COX-2 inhibitors (ibuprofen, naproxen, celecoxib): Caution, acute kidney injury

Heat, sauna, prolonged endurance exercise, or fluid loss: Caution, low blood pressure and kidney injury risk

Licorice root (glycyrrhizin): Caution (theoretical), opposes losartan's effect

Lithium: Monitor, lithium toxicity

Rifampin, milk thistle (silymarin): Monitor, blood pressure control may weaken

Fluconazole (a CYP2C9 inhibitor): Monitor, net blood pressure effect untested

Grapefruit juice: Monitor, clinical impact likely small

Other blood pressure-lowering drugs (amlodipine, hydrochlorothiazide, metoprolol): Monitor, dizziness or fainting

PDE5 inhibitors (sildenafil, tadalafil), alpha-blockers (tamsulosin, doxazosin), alcohol: Monitor (theoretical), dizziness or fainting

Blood pressure-lowering supplements (garlic extract, beetroot nitrate, magnesium, coenzyme Q10, fish oil, hibiscus): Monitor (theoretical), dizziness

Decongestants (pseudoephedrine, phenylephrine): Monitor (theoretical), may offset losartan's effect

St John's wort: Monitor (theoretical), could alter blood pressure control

Risk & Side Effects

High: High blood potassium

Medium: Low blood pressure and dizziness; kidney function decline; lower hemoglobin

Low: Fetal injury and death; cancer; angioedema (sudden deep swelling of face or throat); nitrosamine impurity exposure

Speculative: Blunted muscle growth from strength training

Monitoring

Marker	Target	Why
Blood pressure (home, seated)	<130/80 mmHg	Main treatment effect
Serum potassium	3.5–5.0 mmol/L	Safety check: a rise above range changes dose or use
Serum creatinine and eGFR (kidneys' filtering capacity)	Creatinine about 0.7–1.3 mg/dL (men), 0.6–1.1 mg/dL (women); eGFR: no established target	Safety check: a rise of more than 30% within 4 weeks prompts dose review
Urine albumin-to-creatinine ratio (UACR)	<30 mg/g	Expected to fall with losartan
Serum uric acid	<6 mg/dL	Losartan lowers it modestly
Hemoglobin	13.5–17.5 g/dL (men), 12.0–15.5 g/dL (women)	Safety check: a meaningful fall prompts review
Pregnancy test	Negative	Safety check: a positive result stops use

Cadence: Baseline before starting; potassium and creatinine within 2–4 weeks of starting or any dose increase, again at 3 months, then every 6–12 months; home blood pressure several times weekly during titration and weekly once stable; urine albumin, uric acid, and hemoglobin every 12 months

Qualitative Assessment

Dizziness or light-headedness on standing
Energy, fatigue, and exercise tolerance
Muscle cramps or weakness (possible potassium change)
Swelling of lips, tongue, face, or throat (a possible sign of angioedema)
Sleep quality and nighttime urination
Cognitive clarity and mood

Losartan for Health & Longevity

Protocol

Benefits

Risk & Side Effects

Monitoring

Qualitative Assessment