Heart rate in the Mounjaro® documents
Palpitations, the feeling of a pounding, racing or fluttering heart, are not listed as such. What the documents report is a measured rise in heart rate and episodes of a fast regular rhythm, called sinus tachycardia [1][3][4].
| Measure | Placebo | 5 mg | 10 mg | 15 mg |
|---|---|---|---|---|
| US: sinus tachycardia with a rise of 15+ beats per minute, diabetes trials [1] | 4.3% | 4.6% | 5.9% | 10% |
| US: same, patients enrolled in Japan [1] | 7% | 7.1% | 9.3% | 23% |
| EU: rise of more than 20 beats on 2+ visits, diabetes trials [3] | 2.1% | 2.1% | 3.8% | 2.9% |
| EU: same, weight-management trial without diabetes [3] | 1.2% | 2.4% | 4.9% | 6.3% |
| EU: arrhythmia and conduction events, diabetes trials [3] | 3% | 3.8% | 2.1% | 3.7% |
Average rise against individual episodes
On average the change is small. In the US diabetes pool, heart rate rose by 2 to 4 beats per minute on Mounjaro® and by 1 on placebo [1]; Europe reports a maximum average rise of 3 to 5 beats in the same type of trials, 6 beats in SURPASS-CVOT, the long heart-outcomes trial, and 2 to 3 beats in its weight-management, sleep apnoea and heart failure trials [3]. The US label says the clinical relevance of these increases is uncertain [1].
Averages can hide individuals. The share of people with episodes of a clearly faster rate climbs with dose, reaching 10% on 15 mg in the US pool and 23% among the 43 people on 15 mg enrolled in Japan [1]. In Europe’s weight-management trial, sustained rises of more than 20 beats were about five times more common on 15 mg than on placebo [3]. Rhythm and conduction problems, by contrast, were reported at similar rates on tirzepatide and placebo, and the small changes in the PR interval on the heart tracing were not judged meaningful [3][4].
What larger analyses show
A network meta-analysis of tirzepatide trials in type 2 diabetes found heart rate rose by about 1.8 beats more than with comparators overall, and that 15 mg raised it more than 5 mg or 10 mg, GLP-1 medicines, insulin or placebo, which the authors described as a dose-response effect [5]. A separate meta-analysis of 12 trials with 10,615 people with diabetes found no significant increase in atrial fibrillation or atrial flutter, though dizziness was more common [6].
Outside trials, a 2026 study of US spontaneous reports for tirzepatide found no excess reporting of tachycardia or atrial fibrillation in reports from doctors and pharmacists; a tachycardia signal seen in the full data set was not confirmed in those professional reports [7]. A single published case describes a young woman whose postural orthostatic tachycardia syndrome, a condition where the heart races on standing, flared while she used tirzepatide for weight loss [8]. A case report cannot show how often this happens.
Listed effects that can make the heart race
- Low blood sugar: fast heartbeat is among its warning signs, with shakiness, sweating, hunger and confusion. The risk is highest when Mounjaro® is combined with insulin or a sulfonylurea [1][2][10].
- Dehydration: vomiting and diarrhea can lead to fluid loss, and a rapid heartbeat is a sign of severe dehydration [1][11].
- Serious allergic reaction: a very rapid heartbeat together with swelling of the face or throat, breathing trouble or fainting [2].
- Low blood pressure: Europe lists hypotension as common in people treated for weight management [3]. MedlinePlus counts dizziness or lightheadedness alongside palpitations as a reason for urgent care [9].
Other causes of palpitations
MedlinePlus lists anxiety and stress, caffeine, nicotine, alcohol, fever, exercise, decongestants such as pseudoephedrine, diet pills and stimulant drugs [9]. Some palpitations come from an abnormal rhythm linked to heart disease, valve problems, abnormal potassium levels, an overactive thyroid, low blood oxygen or certain medicines for asthma, blood pressure or heart conditions [9].
Canada specifically asks for caution when Mounjaro® is combined with other medicines that raise heart rate, such as those with sympathomimetic or anticholinergic effects [4]. A pharmacist can check your list, including cold remedies.
Steps that general guidance describes
The Mounjaro® documents do not give self-care advice for palpitations. MedlinePlus describes general steps once a serious cause has been ruled out by a clinician.
- Cut back on caffeine, nicotine and other stimulants, which often reduces palpitations [9].
- Relaxation or breathing exercises, yoga, meditation or tai chi may help with stress-related palpitations [9].
- If you use insulin or a sulfonylurea, check your blood sugar when your heart races, as your diabetes team has advised, and follow your plan for lows [1][10].
- Keep up fluids on days with vomiting or diarrhea, and call your provider if you cannot [2][11].
- Note when episodes happen, how long they last and whether the rhythm feels regular, which a clinician will ask about [9].
Mounjaro® is a registered trademark of Eli Lilly and Company. PepLabo is not affiliated with or endorsed by Eli Lilly and Company.
When to get help
| Sign | Who to contact | How fast | Source |
|---|---|---|---|
| Palpitations with chest pain, shortness of breath, fainting, unusual sweating or dizziness | Emergency services (911 in the US, 112 in Europe) | Emergency | MedlinePlus [9] |
| A very rapid heartbeat with swelling of the face, lips or throat, or trouble breathing | Stop Mounjaro® and get medical help right away | Emergency | Medication Guide [2] |
| Racing heart with shakiness, sweating, hunger or confusion, especially on insulin or a sulfonylurea | Treat as low blood sugar per your plan; seek help if it does not improve | Emergency | Medication Guide [2]; MedlinePlus [10] |
| New or different palpitations, a resting pulse over 100 without fever or exercise, or palpitations when you have heart disease or diabetes | Your provider right away | Today | MedlinePlus [9] |
| A heart condition that a faster heart rate could worsen, before or during treatment | Discuss with your prescriber | At your next appointment | Canadian monograph [4] |
