Based on NIH | Is constipation a side effect of omeprazole, and how common is it?

Omeprazole can cause constipation, and it appears to be an uncommon but recognized side effect. ^[1] In clinical studies summarized in the official U.S. prescribing information, constipation occurred in about 1% to 2% of people taking omeprazole, placing it among the less frequent adverse effects. ^{[2] [3] [4]} In practical terms, that means roughly 1 to 2 out of 100 users may experience constipation while on the medication. ^{[5] [6]}

How common is constipation with omeprazole?

• Constipation is listed as an adverse reaction with an incidence around 1% to 2% in omeprazole clinical trials. ^{[2] [3]}
• Multiple versions of the official product label consistently report constipation at approximately 1%–2%. ^{[4] [5] [6]}
• Consumer-facing drug information also lists constipation as a possible side effect that may occur and usually is not severe. ^[1] Overall, constipation is considered uncommon compared with more frequent side effects like headache, abdominal pain, nausea, diarrhea, and gas. ^{[3] [4]}

Quick reference: reported rates

Adverse effect (omeprazole)	Approximate frequency in trials
Headache	~7% [3]
Abdominal pain	~5% [3]
Nausea	~4% [3]
Diarrhea	~4% [3]
Vomiting	~3% [3]
Gas (flatulence)	~3% [3]
Constipation	~1%–2% [2] [3] [4]

Why might PPIs contribute to constipation?

While the exact mechanism isn’t fully defined, proton pump inhibitors (PPIs) like omeprazole can slow the stomach’s processing of solid food by reducing acid-dependent digestion, which may contribute to altered bowel habits for some people. ^[7] This delay in the movement of solid meals through the stomach could, in some individuals, translate into sensations of slowed gut transit and constipation. ^[7]

When to seek medical advice

• If constipation is mild and short-lived, it often improves with simple measures such as hydration, fiber, and gentle activity. ^[1]
• If constipation is persistent, severe, or accompanied by red flags (e.g., blood in stool, severe abdominal pain, vomiting, unexplained weight loss), you should seek medical evaluation promptly. ^[1]
• If constipation began after starting omeprazole and does not improve, your clinician may consider dose adjustment, timing changes, or a different therapy based on your condition and risk profile. ^[1]

Practical tips to reduce constipation risk

• Increase fluid intake unless restricted for other medical reasons. ^[1]
• Add dietary fiber gradually (whole grains, fruits, vegetables) and consider a fiber supplement if needed. ^[1]
• Stay physically active as tolerated to stimulate bowel movement. ^[1]
• Review other constipating medicines (e.g., certain pain relievers or anticholinergic drugs) with your clinician, as combined effects can worsen constipation. ^[8]

Bottom line

Constipation is a documented side effect of omeprazole, occurring in about 1% to 2% of users based on clinical trial data and official labeling. ^{[2] [3] [4] [5] [6]} Most cases are mild, but persistent or severe symptoms warrant medical advice to consider supportive care or alternative treatment. ^[1]