A Lithium GLP-1 Interaction

More evidence of a serious drug interaction

STUDY: Patarroyo-Rodriguez LP et al, J Clin Psychopharmacol 2026

STUDY TYPE: Case report

FUNDING: National Center for Advancing Translational Science (NCATS)

Background

GLP-1 and GIP/GLP-1 receptor agonists like tirzepatide (Mounjaro, Zepbound) cause nausea, vomiting, and dehydration, especially during dose escalation. Dehydration reduces kidney function, and lithium depends on the kidneys for clearance.

Other reports of interactions have involved semaglutide, summarized in the table above.

The Case

• A 55-year-old man with bipolar I disorder, stable on lithium 1200 mg daily for nearly a decade. Last lithium level: 1.0 mEq/L six months prior.
• He obtained tirzepatide 2.5 mg weekly through an unsupervised online platform, then escalated to 5 mg weekly three weeks before hospitalization.
• Concurrent exposures: Regular ibuprofen and naproxen use, 2–4 alcoholic drinks daily.
• No lithium levels were checked after tirzepatide was started.

After the dose increase, he developed nausea, vomiting, and poor oral intake. Within weeks he was confused, disoriented, and tremulous. His lithium level on arrival was 4.1 mEq/L. Kidney function had deteriorated sharply, with creatinine rising to 2.51 mg/dL. Three hemodialysis sessions over 48 hours brought the lithium level down to 0.3 mEq/L and creatinine returned to baseline. Delirium resolved over eight days, though short-term memory impairment lingered.

Limitations

This is a single case with multiple compounding factors: NSAIDs, heavy alcohol use, and an unsupervised dose escalation. The relative contribution of each factor can’t be separated.

Practice Implications

1. GLP-1’s can raise lithium levels, though the interaction is rare and the cause is not known.
2. Most cases occur within a month of starting the GLP-1. Check lithium levels and warn patients of toxicity signs after starting one.