Trulicity® (dulaglutide) and constipation

Three regulators, three ways of counting

Each document counts constipation differently. The US label sets a 5% bar for its main table, so constipation appears in the sentence after Table 1, drawn from 1,670 adults on Trulicity® and 568 on placebo who kept the same dose throughout, with average exposure of about 24 weeks. ^[1] The European summary assigns frequency classes from its phase 2 and 3 trials and puts constipation in the common band. ^[3] Canada’s Table 2 is the only one that prints head counts. It includes every event above 1% that emerged during treatment and was more frequent on Trulicity®, whether or not the medicine caused it, and its definition also takes in infrequent bowel movements. ^[4]

What the figures can and cannot tell you

About four people in every hundred on either dose reported constipation in the placebo-controlled pool, roughly five times the placebo rate, and the lower dose did no better than the higher one. ^[1][4] In the longer Canadian pool, which also compares Trulicity® with active treatments, the 1.5 mg figure edged up to 4.9% while 0.75 mg stayed near 3.5%. ^[4] These are counts of people who reported constipation at least once, so they say nothing about how long it lasted or how hard it was. None of the three documents gives constipation a timing pattern; the EU leaflet says nausea, vomiting and diarrhoea usually ease with time, but makes no such remark about constipation. ^[3]

For 3 mg and 4.5 mg, the US label says only that the side-effect profile of the 36-week dose trial matched earlier adult studies; constipation did not reach the 5% needed to enter Table 2. ^[1] Dulaglutide slows stomach emptying, yet the label does not connect that effect to constipation; our Trulicity® nausea page covers the stomach-emptying data in depth. ^[1]

Research beyond the product information

A 2026 meta-analysis of 101 randomised trials, 18 of them with dulaglutide, found that GLP-1 medicines as a group carried a risk ratio of 2.41 for constipation compared with placebo; in head-to-head comparisons, semaglutide had the highest risk. ^[5] Because it pools five medicines, it does not produce a dulaglutide-only rate.

A 2026 new-user cohort study followed adults with type 2 diabetes who began dulaglutide, semaglutide or tirzepatide in routine practice. Its main outcome combined acute pancreatitis, biliary disease, bowel obstruction, gastroparesis and severe constipation. Against dulaglutide, the hazard ratio was 0.96 for semaglutide across 65,238 matched pairs and 0.96 for tirzepatide across 20,893 pairs, which points to similar risk. ^[6] The design is observational, the authors flag possible residual confounding by blood sugar control and body mass index, and the abstract gives no separate result for constipation or obstruction. ^[6]

A small 2025 cross-sectional study from Turin, Italy, looked at the diets of 103 adults with type 2 diabetes, about half of them on a GLP-1 medicine and 40% of those on dulaglutide. None of the GLP-1 users met fibre recommendations, but fibre was low across the whole group and overall diet did not differ by treatment. ^[7] That points to a common dietary gap in diabetes care rather than an effect of the injection.

When a slow bowel becomes a blocked one

The US list of post-approval reports names three related bowel problems: ileus, intestinal obstruction, and severe constipation including faecal impaction. ^[1] Such reports arrive voluntarily from an unknown number of users, so they cannot yield a rate or prove that the medicine was responsible. ^[1] The EU summary lists non-mechanical intestinal obstruction with a frequency it calls not known, and the Canadian monograph does not name ileus or obstruction among its adverse reactions. ^[3][4]

MedlinePlus explains the terms. Ileus means the bowel stops pushing its contents along although nothing is physically in the way, which is what the European word non-mechanical refers to; an obstruction is a partial or complete block. Signs include a swollen, full belly, cramping, being unable to pass gas, nausea, vomiting and constipation. ^[13] Faecal impaction is a large, hard lump of stool stuck in the rectum, usually after long-standing constipation. It can show up as cramps and bloating, straining, or, confusingly, sudden leaks of watery stool. People who move little or take opioid pain medicines are more at risk. ^[12]

Section 5.6 of the US label adds that Trulicity® can cause stomach and bowel reactions that are sometimes severe, and that it is not recommended for people with severe gastroparesis. ^[1] The European summary asks prescribers to watch closely anyone who develops severe gut symptoms on treatment and to reconsider the treatment plan. ^[3] Bloating and stomach pain on Trulicity® have their own pages; this one holds the blockage detail for all three.

Possible reasons, strongest evidence first

• Supported by the label: constipation was reported more often on Trulicity® than on placebo in controlled trials, so the medicine is a plausible cause in its own right. ^[1][4] The label also states that dulaglutide delays stomach emptying, without linking that to constipation. ^[1]
• Suggested but not measured: a 2025 review in Mayo Clinic Proceedings places constipation among the gut effects that 40% to 70% of people on these medicines notice, without separating out why. ^[8] Eating less and lower fibre intake are often mentioned; the Turin diet study found low fibre in everyone, on GLP-1 medicines or not. ^[7]
• General medical knowledge: NIDDK notes that changing how much or what you eat, too little fluid, too little activity, and diabetes itself can each cause constipation, and that several causes often act together. ^[9]

Causes unrelated to the weekly pen

NIDDK lists medicines and supplements that can make constipation worse, among them antacids containing aluminium or calcium, anticholinergic and antispasmodic drugs, anticonvulsants, some antidepressants and medicines for Parkinson’s disease. ^[9] Conditions on its list include an underactive thyroid, disorders of the brain and spine, inflammation from diverticular disease, pelvic floor problems and blockages caused by tumours. ^[9] MedlinePlus adds opioid pain medicines and diarrhoea remedies taken too often. ^[12]

Ignoring the urge to go and changes in daily routine, such as travel, also slow things down. ^[9] NIDDK advises seeing a doctor when self-care does not help or when there is a family history of colon or rectal cancer. ^[9]

Self-care the sources describe

NIDDK’s first steps are dietary: more high-fibre foods, plenty of water and other drinks, particularly when fibre goes up, and regular physical activity. ^[10] It also suggests allowing enough time on the toilet, going as soon as you feel the need, and trying for the same time each day, often after breakfast. ^[10] MedlinePlus adds that fibre is best increased gradually, because a sudden jump can bring bloating and gas. ^[11] The Mayo Clinic Proceedings review likewise puts diet changes and adequate fluids first for gut symptoms on these medicines, with symptom-relief medicines as the next step if problems persist. ^[8]

Over-the-counter options named by NIDDK include fibre supplements, osmotic laxatives, stool softeners and lubricants; it keeps stimulant laxatives for severe constipation or when other measures have failed, and leaves the choice of type to a health professional, so ask your pharmacist. ^[10] MedlinePlus says not to take a laxative if you have severe stomach pain, nausea or vomiting. ^[11] Because Trulicity® slows stomach emptying, the EU leaflet asks you to tell your doctor or pharmacist about every other medicine you use, which includes anything bought for constipation. ^[3] NIDDK also warns against stopping or changing a prescribed medicine without talking to a professional first. ^[10]

Trulicity® is a registered trademark of Eli Lilly and Company. PepLabo is not affiliated with or endorsed by Eli Lilly and Company.