What the label lists and what reports show
Losartan side effects
Losartan's FDA label: “Most common adverse reactions (incidence ≥2% and greater than placebo) are: dizziness, upper respiratory infection, nasal congestion, and back pain.” FAERS holds 200,566 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is fatigue (14,008 reports).
- Generic listed
- Boxed warning
Check it at the source: the losartan FDA label on DailyMed (effective January 20, 2026, Organon LLC); the FDA FAERS public dashboard.
What does the patient leaflet say about side effects?
From the patient leaflet: What are the possible side effects of COZAAR?COZAAR may cause the following side effects that may be serious: Injury or death of unborn babies. See " What is the most important information I should know about COZAAR? " Allergic reaction. Symptoms of an allergic reaction are swelling of the face, lips, throat or tongue. Get emergency medical help right away and stop taking COZAAR. Low blood pressure (hypotension). Low blood pressure may cause you to feel faint or dizzy. Lie down if you feel faint or dizzy. Call your doctor right away. For people who already have kidney problems, you may see a worsening in how well your kidneys work. Call your doctor if you get swelling in your feet, ankles, or hands, or unexplained weight gain. […]
Source: FDA drug label, Organon LLC, effective January 20, 2026 (SPL set 9949448f-c3b9-44ee-94ed-c1aca8c90f39), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsMost common adverse reactions (incidence ≥2% and greater than placebo) are: dizziness, upper respiratory infection, nasal congestion, and back pain.
A table the label prints in its adverse reactions section without a title; its column headings name the groups compared
This table is printed in the Losortan Potassium label published by Proficient Rx LP of November 1, 2019; the label quoted above does not print one.
| Reaction | Losartan and Conventional Antihypertensive Therapy Incidence % (n=751) | Placebo and Conventional Antihypertensive Therapy Incidence % (n=762) |
|---|---|---|
| Asthenia/Fatigue | 14 | 10 |
| Chest Pain | 12 | 8 |
| Fever | 4 | 3 |
| Infection | 5 | 4 |
| Influenza-like disease | 10 | 9 |
| Trauma | 4 | 3 |
| Hypotension | 7 | 3 |
| Orthostatic hypotension | 4 | 1 |
| Diarrhea | 15 | 10 |
| Dyspepsia | 4 | 3 |
| Gastritis | 5 | 4 |
| Diabetic neuropathy | 4 | 3 |
| Diabetic vascular disease | 10 | 9 |
| Cataract | 7 | 5 |
| Sinusitis | 6 | 5 |
| Anemia | 14 | 11 |
| Hyperkalemia | 7 | 3 |
| Hypoglycemia | 14 | 10 |
| Weight gain | 4 | 3 |
| Back pain | 12 | 10 |
| Leg pain | 5 | 4 |
| Knee pain | 5 | 4 |
| Muscular weakness | 7 | 4 |
| Hypesthesia | 5 | 4 |
| Bronchitis | 10 | 9 |
Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.
From the label: adverse reactions, continuedMost common adverse reactions (incidence ≥2% and greater than placebo) are: dizziness, upper respiratory infection, nasal congestion, and back pain. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Organon LLC, a subsidiary of Organon & Co., at 1-844-674-3200 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. Hypertension COZAAR has been evaluated for safety in more than 3300 adult patients treated for essential hypertension and 4058 patients/subjects overall. Over 1200 patients were treated for over 6 months and more than 800 for over one year. Treatment with COZAAR was well-tolerated with an overall incidence of adverse events similar to that of placebo. In controlled clinical trials, discontinuation of therapy for adverse events occurred in 2.3% of patients treated with COZAAR and 3.7% of patients given placebo. In 4 clinical trials involving over 1000 patients on various doses (10-150 mg) of losartan potassium and over 300 patients given placebo, the adverse events that occurred in ≥2% of patients treated with COZAAR and more commonly than placebo were: dizziness (3% vs. …
Source: FDA drug label, Organon LLC, effective January 20, 2026 (SPL set 9949448f-c3b9-44ee-94ed-c1aca8c90f39), via openFDA; the full label on DailyMed
What do FAERS reports show?
200,566 reports list losartan among the medicines taken, each a report of something that happened, not proof the medicine caused it; 14,810 are coded as a death and 60,827 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 21 reactions below, 14 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
Reports received each year
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Losartan: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions