Metformin and a GLP-1 receptor agonist are one of the most common drug pairings in type 2 diabetes. A case report and literature review published in Kidney360 describes what happens when that combination goes wrong: a 59-year-old woman developed severe metformin-associated lactic acidosis alongside ketoacidosis, while her blood glucose stayed close to normal — the very reading that would ordinarily push clinicians away from the diagnosis. She survived after emergency dialysis. The authors’ argument is that the pattern is recognisable, and easy to miss.
How the two problems combine
Metformin-associated lactic acidosis (MALA) is rare and dangerous: the authors put its incidence at fewer than 10 cases per 100,000 patient-years, with mortality of 30 to 50 percent. It usually appears alongside acute kidney injury, which stops the kidneys clearing metformin; the accumulating drug inhibits mitochondrial complex I, shifting pyruvate metabolism toward lactate. Euglycemic diabetic ketoacidosis is a separate problem, classically defined as ketoacidosis with blood glucose below 250 mg/dL. It is best known with SGLT2 inhibitors, but the authors note it is increasingly recognised with GLP-1 receptor agonists too, arriving through appetite suppression, vomiting and reduced intake rather than through insulin failure.
What links the two is a single ordinary trigger: not eating and not drinking. The nausea and vomiting that are the most commonly reported complaints on these drugs are the same events that dehydrate a patient, reduce kidney perfusion, impair metformin clearance and start ketone production. The patient in this report was taking metformin and tirzepatide, and was treated with emergency sequential haemodialysis followed by high-dose continuous venovenous haemodiafiltration. Concurrent MALA and ketoacidosis with relative euglycemia is, the authors write, exceedingly rare, and no published synthesis of such cases existed to guide recognition or management — which is why they paired the case with a review of previously reported MALA cases involving GLP-1 receptor agonists.
The practical point is diagnostic. A glucose reading that looks reassuring is the thing most likely to delay the right test. The authors’ stated lesson is that in a patient taking both metformin and a GLP-1 receptor agonist, gastrointestinal side effects can precipitate MALA, while a disproportionately low glucose can mask the ketoacidosis accompanying it. Their recommendation is early measurement of serum beta-hydroxybutyrate and prompt initiation of renal replacement therapy. For anyone taking both drugs, that reframes a stomach bug or a run of severe vomiting from an inconvenience into a reason to seek care rather than wait it out.
What this does not establish
This is one patient plus a review of published cases, and that design cannot produce a risk estimate. There is no denominator, so nothing here shows that adding a GLP-1 receptor agonist to metformin raises the chance of lactic acidosis; it shows a mechanism by which the two can coincide. Case reports are also selected for publication precisely because they are dramatic, which inflates how common a pattern looks. The abstract does not state how many earlier cases the review pooled, and a single case cannot separate tirzepatide from the wider drug class. It is worth holding the baseline in view: at fewer than 10 cases per 100,000 patient-years, MALA is uncommon even among the very large number of people taking metformin. We have read the published abstract in full, not the complete paper.
Sources: Adnani H, et al. Metformin-Associated Lactic Acidosis and Relative Euglycemic Ketoacidosis Precipitated by a Glucagon-Like Peptide-1 Receptor Agonist: A Case Report and Literature Review. Kidney360, 2026. PMID 42696402.
