What the label lists and what reports show

Lactulose side effects

Lactulose's FDA label lists its adverse reactions in its own words. FAERS holds 38,214 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 nausea (2,625 reports).

Generic listed

Check it at the source: the lactulose FDA label on DailyMed (effective January 28, 2026, Chartwell RX, LLC); the FDA FAERS public dashboard.

What does the label list?

From the label: adverse reactions
Precise frequency data are not available. Initial dosing may produce flatulence and intestinal cramps, which are usually transient. Excessive dosage can lead to diarrhea with potential complications such as loss of fluids, hypokalemia, and hypernatremia. Nausea and vomiting have been reported. To report SUSPECTED ADVERSE REACTIONS, contact Chartwell RX, LLC. at 1-845-232-1683 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

Source: FDA drug label, Chartwell RX, LLC, effective January 28, 2026 (SPL set d6975cd8-80e0-43e2-809a-175ea7e40715), via openFDA; the full label on DailyMed

What do FAERS reports show?

38,214 reports list lactulose among the medicines taken, each a report of something that happened, not proof the medicine caused it; 6,670 are coded as a death and 20,957 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, 3 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

Nausea (named in the label)2,625
Constipation (a use or a product term, not a reaction)2,572
Fall2,306
Vomiting (named in the label)2,142
Fatigue2,099
Death (an outcome recorded in the report)2,004
Diarrhoea (named in the label)1,968
Dyspnoea1,961
Pain1,754
Pneumonia1,740
Off Label Use (a use or a product term, not a reaction)1,658
Hypotension1,565
Confusional State1,515
Pyrexia1,430
Asthenia1,378
Abdominal Pain1,325
Malaise1,265
Headache1,251
Dizziness1,248
Acute Kidney Injury1,230
Drug Ineffective (a use or a product term, not a reaction)1,193
Anaemia1,167
Weight Decreased994
Urinary Tract Infection989
Balance Disorder980

Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms

What next?

Lactulose: 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