Mounjaro® and dizziness

The labels, read together

In the US, Mounjaro® is a once-weekly tirzepatide injection for type 2 diabetes, including in children 10 and older, and for lowering cardiovascular risk in adults with type 2 diabetes at high risk ^[1]. Dizziness is not among the reactions in its main safety table or postmarketing list ^[1]. It appears in the Medication Guide in two other places: as a sign of low blood sugar and as part of a serious allergic reaction ^[2].

The European product information pools 14 phase 3 studies in 15,169 adults, including weight-management trials. It places both dizziness and hypotension (low blood pressure) in the “common” column and adds a footnote that both mainly apply to people with overweight or obesity, with or without diabetes ^[3]. The patient leaflet describes dizziness and low blood pressure as reported in people treated for weight management ^[3].

The Canadian monograph does not include dizziness in its table of reactions, but its patient information lists feeling dizzy or lightheaded among the signs of dehydration that can lead to sudden kidney failure ^[4].

Evidence from trials and real-world data

The most relevant study for Mounjaro® users is a 2025 meta-analysis of 12 randomised trials with 10,615 people with type 2 diabetes ^[6]. Tirzepatide raised the risk of dizziness compared with the control groups (risk ratio 1.64, 95% CI 1.04 to 2.57), with a higher risk in people aged 60 or younger. It did not raise the risk of headache or transient ischaemic attack.

For weight reduction, the Zepbound® label adds detail on blood pressure: low blood pressure occurred in 1.6% on tirzepatide against 0.1% on placebo, more often in people already taking blood pressure medicines (2.2% versus 1.2% of those not taking them), and also in connection with stomach side effects and dehydration ^[5].

A large US health-record study compared new users of semaglutide and tirzepatide with matched controls and found more new diagnoses of vestibular (inner-ear balance) disorders in both ^[7]. For tirzepatide the absolute numbers were small, rising from 0.10% at six months to 0.19% at three years, against 0.04% to 0.15% in controls, and lower than with semaglutide. Being retrospective, it cannot prove cause.

An analysis of FDA adverse event reports for six GLP-1-based medicines, tirzepatide among them, found reporting signals for dizziness and presyncope (feeling about to faint), with about 45% of neurological reports arising within the first month ^[8]. The authors stress that these are associations, not causal findings.

Three causes to tell apart

Low blood sugar. The US label warns that Mounjaro® with insulin or a sulfonylurea increases the risk of low blood sugar, including severe episodes ^[1]. When Mounjaro® was added to basal insulin, readings below 54 mg/dL occurred in 14% to 19% of people on the three doses against 13% on placebo ^[1]. Dizziness tends to come with sweating, shakiness, hunger, a fast heartbeat, blurred vision or confusion ^[2][11].

Fluid loss. Vomiting, diarrhea and drinking less can lead to dehydration, which the label links to kidney injury ^[1]. Here dizziness is more likely with thirst, a dry mouth and dark, strong-smelling urine ^[4].

Low blood pressure. Tirzepatide’s weight-loss label records it more often in people already on blood pressure tablets, and MedlinePlus lists those tablets and dehydration among its causes ^[5][10]. MedlinePlus describes this type as lightheadedness that comes on when you stand up from sitting or lying ^[9][10].

Supported versus proposed: the first two routes are written into the Mounjaro® labels; the blood pressure route is documented for tirzepatide in weight-management populations ^[3][5]. Why inner-ear balance disorders might be more common with these medicines is not known ^[7].

Other causes of dizziness

MedlinePlus separates lightheadedness (feeling you might faint) from vertigo (a spinning sensation). Lightheadedness can follow a cold or flu, allergies or medicines that lower blood pressure; vertigo is often caused by inner-ear problems such as benign positional vertigo, labyrinthitis or Ménière disease ^[9].

Less often, dizziness reflects heart rhythm problems, a heart attack, stroke or internal bleeding, usually with other symptoms such as chest pain, a racing heart, slurred speech or vision change ^[9]. That is why new dizziness with any of those features is treated as an emergency.

What helps in the moment and over time

If you use insulin or a sulfonylurea and feel dizzy, checking your blood sugar is the first step; MedlinePlus describes treating a low with a sugary drink, food or glucose tablets as your care team has taught you ^[11]. Before starting Mounjaro®, the Medication Guide asks you to discuss low blood sugar and how to manage it ^[2].

For lightheadedness on standing, MedlinePlus suggests getting up slowly, sitting for a moment before standing, and holding on to something; during a spinning spell, keep still, avoid sudden movements and do not drive or climb ^[9]. When dehydration lies behind low blood pressure, MedlinePlus notes that a clinician may suggest drinking more fluids ^[10].

The European label says tirzepatide has little or no effect on the ability to drive, but advises precautions against low blood sugar while driving if it is combined with a sulfonylurea or insulin ^[3]. Adjusting insulin, sulfonylurea or blood pressure tablets is a decision for your prescriber.

Mounjaro® and Zepbound® are registered trademarks of Eli Lilly and Company. PepLabo is not affiliated with or endorsed by Eli Lilly and Company.