Based on NIH | Is diarrhea a known side effect of Losartan, and how common is it?

Yes diarrhea is a recognized side effect of losartan, though it is generally uncommon in the broader hypertension population and more prominently reported in a specific subgroup. ^[1] In consumer and professional labeling for Cozaar (losartan), diarrhea is listed among the most common side effects for people with type 2 diabetes who have diabetic kidney disease (diabetic nephropathy). ^{[2] [3]} In contrast, across general hypertension trials, overall adverse event rates with losartan were similar to placebo, suggesting diarrhea occurs infrequently in the wider user base. ^[4]

What official information says

• The U.S. drug label for losartan lists diarrhea as a possible side effect and specifically highlights it as one of the most common effects in adults with type 2 diabetes and kidney disease treated with losartan. ^{[5] [6]}
• MedlinePlus, a trusted drug-information resource, also lists diarrhea as a possible side effect of losartan. ^[1]

How common is it?

• In large, double‑blind clinical trials of losartan for uncomplicated hypertension, the overall adverse event profile was similar to placebo, with dizziness being the only patient‑reported, drug‑related effect occurring more often than placebo at a low rate (about 2.4% vs 1.3%); these summaries do not single out diarrhea as a frequent signal in the general population. ^[4]
• In labeling focused on diabetic nephropathy, diarrhea is called out among the “most common” side effects in that subgroup, indicating a higher relative frequency in these patients compared with other settings. ^{[2] [3]}
• While the professional label includes a tabulated adverse-event section that lists gastrointestinal events (including diarrhea) observed in trials, the available consumer-facing sections emphasize that diarrhea is a commonly reported effect specifically in the diabetic kidney disease population. ^{[7] [6]}

Context among ARBs

• Diarrhea has been reported with several angiotensin receptor blockers (ARBs) at low rates; for example, irbesartan trials reported diarrhea in about 3% of treated patients vs 2% with placebo, reflecting a small absolute difference. ^{[8] [9]}
• Notably, rare, severe sprue‑like enteropathy has been linked to olmesartan, but broader evaluations did not find a general association between ARB use and chronic diarrhea in endoscopy populations, suggesting such reactions are uncommon. ^[10]

Practical takeaways

• For most people taking losartan for high blood pressure, diarrhea appears to be an uncommon side effect and may not occur at a rate higher than placebo. ^[4]
• For adults with type 2 diabetes and diabetic kidney disease on losartan, diarrhea is described as one of the more common side effects in official materials, so it may be encountered more often in this subgroup. ^{[2] [3]}
• If diarrhea occurs, it is often mild and temporary, but persistent symptoms, signs of dehydration, or severe gastrointestinal distress warrant medical review and possible adjustment of therapy. ^[1]

Quick reference table

Setting	Is diarrhea listed?	How it’s characterized	Notes
General hypertension population (mixed trials)	Yes	Uncommon; overall adverse events similar to placebo	Dizziness was the notable drug-related event > placebo; diarrhea not highlighted as frequent in this group. [4]
Type 2 diabetes with diabetic kidney disease	Yes	Listed among the most common side effects	Specifically called “most common” in this subgroup in Cozaar labeling. [2] [3]
Other ARBs (example: irbesartan)	Yes	Low absolute rates (e.g., 3% vs 2% placebo)	Indicates diarrhea can occur with ARBs but typically at low frequency. [8] [9]

When to contact a clinician

• If diarrhea is persistent, severe, or accompanied by weakness, lightheadedness, or reduced urination (possible dehydration), you should seek medical advice. ^[1]
• Sudden onset of severe abdominal symptoms, blood in stool, or significant weight loss should be evaluated promptly. ^[1]

In summary, diarrhea is a known side effect of losartan. ^[1] It appears relatively uncommon in the general hypertension population but is highlighted as one of the more common effects in people with type 2 diabetes and diabetic kidney disease who use losartan. ^{[4] [2] [3]}