Glimepiride: how it works, cautions and side effects

Glimepiride is a sulfonylurea used for type 2 diabetes in adults when changes to diet, activity and weight have not brought blood sugar under control. This guide is based on the emc summary of product characteristics for glimepiride tablets, because a dedicated NHS patient page was not available when checked.

It works mainly by prompting the insulin-producing beta cells in the pancreas to release more insulin. The product information also describes smaller effects outside the pancreas: improved tissue sensitivity to insulin and reduced glucose output from the liver.

Glimepiride is a once-a-day tablet. The SmPC says to take it shortly before or during a substantial breakfast or, if no breakfast is eaten, the first main meal of the day, and to swallow the tablets whole with some liquid. A matching meal is part of the plan.

Prescribers begin with a low dose and raise it at intervals of one to two weeks depending on blood sugar results. The SmPC says doses beyond a certain level rarely give additional benefit. Because the right amount differs between people, follow your prescriber and the leaflet.

Low blood sugar is the most important practical risk. The SmPC states that meals taken at irregular times or skipped altogether can cause it, and lists headache, tremor and confusion, up to coma, as possible features. Older adults, people who are undernourished, and people with impaired kidney function are described as more susceptible.

Practical consequences: keep to a regular meal pattern, carry fast-acting sugar, and make sure family or colleagues know what a hypo looks like. Ask your diabetes team about driving if lows are frequent.

The SmPC lists allergy to glimepiride, other sulfonylureas or sulfonamides, type 1 diabetes, diabetic coma or ketoacidosis, and severe kidney or liver dysfunction (where insulin is needed instead) as contraindications. People with G6PD deficiency can develop haemolytic anaemia on sulfonylureas, so non-sulfonylurea options are recommended. Tablets contain lactose, which matters for those with certain rare intolerances.

Care typically includes blood and urine glucose checks and HbA1c measurement, plus liver and blood-count monitoring. The SmPC lists as rare effects low platelet or white cell counts, hypoglycaemia, taste change, hair loss and weight gain. Very rare effects include more severe blood disorders, nausea, vomiting, diarrhoea and liver dysfunction; others of unknown frequency include vasculitis, visual disturbance and allergic skin reactions such as rash, hives and photosensitivity.

Yellow skin, unexplained bruising, sore throat or fever deserve prompt medical review; severe allergic symptoms need emergency help.

Glimepiride is processed by the CYP2C9 enzyme, so several medicines change its strength. The SmPC says effects can be increased by insulin, metformin, salicylates, anabolic steroids, some antibiotics, anticoagulants, ACE inhibitors, fluconazole and allopurinol. Effects can be reduced by oestrogens, thiazide diuretics, glucocorticoids, phenytoin, rifampicin and barbiturates. Beta blockers, H2 antagonists and alcohol can go either way.

The colesevelam bile acid binder reduces absorption, and the SmPC says to take glimepiride at least four hours before it.

Glimepiride is contraindicated in pregnancy because of animal reproductive toxicity, and insulin is used instead. Breastfeeding is advised against because of the hypoglycaemia risk in infants. Blood sugar that is too high or too low can impair concentration, so take precautions before driving.

It is a prescription-only medicine. Suspected side effects can be reported to the Yellow Card scheme.