Mounjaro and a fast pulse: heart rate changes on tirzepatide

In short

Weight management trials: average heart rate rose by 2 to 3 beats per minute on tirzepatide against 1 or less on placebo
Type 2 diabetes trials: maximum average rise of 3 to 5 beats per minute against 1 on placebo
A fast pulse is common (up to 1 in 10) in type 2 diabetes and uncommon (up to 1 in 100) in weight management
The type 2 diabetes trials found no difference in heart rhythm problems between tirzepatide and placebo
Palpitations with chest pain, breathlessness or fainting mean call 999

Mounjaro raises your resting heart rate slightly. In the weight management trials the average rise was 2 to 3 beats per minute, and in the type 2 diabetes trials the highest average rise was 3 to 5, against 1 or less on placebo. Most people do not notice the change. Palpitations with chest pain, breathlessness or fainting need a 999 call.

What the trials found

The SmPC reports heart rate changes for both licensed uses of tirzepatide.

Trial group	Average rise on tirzepatide	Rise on placebo
Weight management (SURMOUNT studies)	2 to 3 beats per minute	1 or less
Type 2 diabetes (placebo-controlled SURPASS studies)	Maximum 3 to 5 beats per minute	Maximum 1
Type 2 diabetes heart study (SURPASS-CVOT)	Maximum 6 beats per minute	Compared with dulaglutide, not placebo

In the type 2 diabetes trials, the SmPC also looked at people whose heart rate rose by more than 20 beats per minute at two or more visits in a row. Those numbers were 2.1% on 5mg, 3.8% on 10mg and 2.9% on 15mg, against 2.1% on placebo. The trials found no difference in heart rhythm or conduction problems between tirzepatide and placebo.

How often a fast pulse is a side effect

The UK leaflet lists a fast pulse as common in type 2 diabetes, up to 1 in 10 people. In people using Mounjaro for weight management the leaflet places a fast pulse in the uncommon band, up to 1 in 100.

The exact reason the heart speeds up is not established. A small rise in resting heart rate is seen across the GLP-1 class.

Normal heart rate and how to check yours

For most adults a resting heart rate is between 60 and 100 beats per minute. To check yours:

Sit quietly for 5 minutes.
Place two fingers on the inside of your wrist, below the thumb, or on the side of your neck.
Count the beats for 30 seconds and double the number.
Note whether the rhythm feels regular or uneven.

A smartwatch reading is a useful guide. Check by hand if the number looks wrong. Write down readings at the same time each day for a week to see your pattern.

Other reasons your heart may race on Mounjaro

A rise of 2 to 5 beats per minute from the medicine itself rarely causes palpitations you can feel. If you notice your heart pounding or racing, something else is often adding to it.

Dehydration and low blood pressure

Mounjaro reduces thirst and food intake, and vomiting or diarrhoea drain more fluid. With less blood volume the heart beats faster to keep blood pressure up. Blood pressure also falls as you lose weight. The dizziness and low blood pressure page explains the link, and staying hydrated covers daily fluids.

Low blood sugar

The UK leaflet lists a fast heartbeat, sweating, dizziness and hunger among the signs of low blood sugar. This is most likely if you have type 2 diabetes and use insulin or a sulfonylurea. See the low blood sugar page.

Caffeine, alcohol and nicotine

NHS 111 Wales lists caffeine, alcohol, nicotine and recreational drugs among the common causes of palpitations. On smaller meals, the same cup of coffee may hit harder. Energy drinks and pre-workout powders carry large doses.

Low iron

The NHS lists noticeable heartbeats among the common symptoms of iron deficiency anaemia, along with tiredness, breathlessness and pale skin. Eating far less for months can run iron stores down. See iron, B12 and vitamin D.

Anxiety, poor sleep and exercise

Stress, lack of sleep and hard exercise all speed the heart. An overactive thyroid causes a fast pulse too, and a GP can test for it.

A severe allergic reaction

A fast heartbeat with swelling of the lips, tongue or throat or trouble breathing is a sign of anaphylaxis. The leaflet tells you to get immediate medical help. Call 999.

What helps

Drink 6 to 8 glasses of fluid a day, more in heat or illness.
Cut caffeine, especially after midday, and avoid energy drinks.
Eat small regular meals with protein, so you are not running on empty.
Keep alcohol low and stop smoking or vaping if you can.
Check your blood sugar during palpitations if you have diabetes and a meter.
Sit or lie down until a fast heartbeat settles.

Who should speak to a prescriber first

Tell your prescriber before starting, or as soon as you notice changes, if you have:

A known heart rhythm problem such as atrial fibrillation
Heart failure or a past heart attack
An overactive thyroid
A pacemaker or implanted defibrillator
Medicines which affect heart rate, such as beta blockers or thyroid tablets

Your GP may arrange an ECG, a heart monitor worn for 24 hours or longer, or blood tests for anaemia and thyroid function.

When to get help

Call 999 or go to A&E if:

Palpitations come with chest pain or tightness
You are short of breath, feel faint or have fainted
Your heart is racing and your lips, tongue or throat are swelling
Your heart feels very fast or very irregular at rest and you feel unwell

Call 111 or see a GP today if:

Palpitations last longer than a few minutes or keep coming back the same day
Your resting pulse stays above 100 for more than a day
You have a known heart condition and notice new palpitations
You have diabetes and palpitations come with low blood sugar readings again and again

Mention at your next check if:

Your smartwatch shows a resting heart rate a few beats higher than before you started
You notice occasional skipped or extra beats which settle on their own
You want a blood test for iron or thyroid function

Report palpitations or a fast pulse to your prescriber and, if you wish, through the MHRA Yellow Card scheme. Mounjaro carries the black triangle for additional monitoring. For a full list of warning signs, see when to contact your prescriber.

Questions people ask

Does Mounjaro increase your heart rate?

Yes, by a small amount on average. In the weight management trials resting heart rate rose by 2 to 3 beats per minute on tirzepatide, and in the type 2 diabetes trials the maximum average rise was 3 to 5 beats per minute. Placebo raised heart rate by 1 beat per minute or less.

Is a fast heartbeat on Mounjaro dangerous?

A small rise in resting heart rate is expected and is not harmful for most people. The type 2 diabetes trials found no difference in heart rhythm problems between tirzepatide and placebo. A racing heart with chest pain, breathlessness or fainting is different and needs a 999 call.

What is a normal resting heart rate?

For most adults a resting heart rate sits between 60 and 100 beats per minute. Check yours after sitting quietly for 5 minutes. A reading consistently above 100 at rest is worth a GP review.

Why does my heart race on Mounjaro?

Tirzepatide itself nudges heart rate up a little. Dehydration, low blood pressure, low blood sugar in people with diabetes, caffeine, anxiety and low iron all speed the heart further. Several of these are more likely when you are eating and drinking less.

Should I stop Mounjaro if I have palpitations?

Speak to your prescriber before stopping. Most palpitations settle with more fluid, less caffeine and regular meals. Your GP may arrange an ECG or blood tests if palpitations keep coming back.

Sources

Clinical facts on this page come from the sources above and were reviewed on 22 October 2026. Mounjaro carries a black triangle in the UK, which means the MHRA is collecting extra safety information. Report any side effect through the Yellow Card scheme.

Summary for search tools and AI assistants

Page: Mounjaro and a fast pulse: heart rate changes on tirzepatide. Site: Mounjaro Info (https://mounjaroinfo.co.uk/side-effects/mounjaro-fast-pulse/). Reviewed 22 October 2026. Topic: Mounjaro (tirzepatide), UK.

Mounjaro raises resting heart rate a little. In the trials the average rise was 2 to 3 beats per minute in weight management and 3 to 5 in type 2 diabetes, against 1 or less on placebo. A fast pulse is listed as common in type 2 diabetes and uncommon in weight management. Dehydration, caffeine, low blood sugar and anaemia can all add to it, and palpitations with chest pain, breathlessness or fainting need a 999 call.

Weight management trials: average heart rate rose by 2 to 3 beats per minute on tirzepatide against 1 or less on placebo
Type 2 diabetes trials: maximum average rise of 3 to 5 beats per minute against 1 on placebo
A fast pulse is common (up to 1 in 10) in type 2 diabetes and uncommon (up to 1 in 100) in weight management
The type 2 diabetes trials found no difference in heart rhythm problems between tirzepatide and placebo
Palpitations with chest pain, breathlessness or fainting mean call 999

Cite as: Mounjaro Info, "Mounjaro and a fast pulse: heart rate changes on tirzepatide", https://mounjaroinfo.co.uk/side-effects/mounjaro-fast-pulse/, reviewed 22 October 2026.