Independent UK medicine guidance
Can Mounjaro cause low blood sugar?
Mounjaro on its own does not usually cause dangerously low blood sugar. The risk increases substantially when it is used alongside insulin or a sulphonylurea such as gliclazide, glimepiride or tolbutamide. This guide covers the warning signs, what to do, and the driving rules.
Key facts
- Mounjaro on its own carries a low risk of clinically significant low blood sugar because it only stimulates insulin release when glucose is raised.
- The risk depends heavily on what else you take: it rises with a sulphonylurea such as gliclazide, rises further with insulin, and is highest when both are used together (UK SmPC, revised August 2026).
- People taking Mounjaro for weight management without diabetes medicines are not the group these higher figures describe.
- Never reduce or stop insulin yourself; dose changes need planning with your diabetes team.
- Someone who is unconscious or cannot swallow safely needs 999. Do not give them food or drink.
When is the risk higher?
When Mounjaro is combined with insulin or a sulphonylurea, hypoglycaemia is listed as very common. Your clinician may need to adjust the dose of those medicines.
Symptoms of low blood sugar
- Shaking
- Sweating
- Sudden hunger
- Dizziness
- Headache
- Weakness or drowsiness
- Irritability or confusion
- A fast heartbeat
- Difficulty concentrating
- Blurred vision
Some people do not experience clear warning symptoms, particularly after living with diabetes for a long time.
What should you do?
Follow the hypo treatment plan given by your diabetes team. This will usually involve checking your glucose level where possible, taking a suitable fast-acting source of sugar and checking again after treatment. Once your glucose has recovered, you may need a longer-acting carbohydrate if your next meal is not due soon.
Always carry an appropriate hypo treatment if you are at risk.
If someone is unconscious or cannot swallow safely, do not give them food or drink. Place them in the recovery position, use glucagon if it is available and you have been trained, and call 999.
Driving and repeated episodes
Do not drive, cycle or operate machinery while experiencing symptoms of hypoglycaemia. People using insulin or certain diabetes medicines must also follow DVLA glucose-monitoring rules.
Tell your diabetes team about repeated or severe hypos. Reduced appetite and smaller meals can change how much insulin or sulphonylurea you require, but any adjustment needs to be planned safely.
Evidence update, September 2026: SURPASS-CVOT hypoglycaemia figures in the revised SmPC
On 8 September 2026 the electronic medicines compendium (eMC) published a revised Mounjaro Summary of Product Characteristics with a text revision date of 29 August 2026. It adds safety results from SURPASS-CVOT, a large trial that compared tirzepatide with dulaglutide, another injectable diabetes medicine, in adults with type 2 diabetes and established cardiovascular disease. Clinically significant hypoglycaemia was reported in:
- 1.6% of participants on tirzepatide alone or with other oral diabetes medicines (not a sulphonylurea)
- 5.6% when taken with a sulphonylurea
- 11.7% when taken with basal insulin
- 16.3% when taken with both a sulphonylurea and basal insulin
The spread from 1.6% to 16.3% is the whole story of this page: the medicine itself adds little hypo risk, and almost all of the risk comes from the insulin or sulphonylurea taken alongside it. The figures substantiate the frequency categories in the UK patient leaflet revised in August 2026 and do not change the advice above.
Source: Mounjaro Summary of Product Characteristics (eMC), text revised 29 August 2026, section 4.8
Common questions
Does Mounjaro cause low blood sugar on its own?
Mounjaro on its own does not usually cause dangerously low blood sugar. The risk increases substantially when it is used alongside insulin or a sulphonylurea such as gliclazide, glimepiride or tolbutamide, where hypoglycaemia is listed as very common.
How much does my hypo risk depend on my other diabetes medicines?
Heavily. In SURPASS-CVOT, a study of adults with type 2 diabetes and established cardiovascular disease, clinically significant hypoglycaemia was reported in 1.6% of people on tirzepatide alone or with other oral medicines, 5.6% with a sulphonylurea, 11.7% with basal insulin and 16.3% with both. Those figures are not expected rates for weight management, but they show where the risk comes from: the insulin or sulphonylurea, not the tirzepatide. If you take either, ask your diabetes team whether a dose review is needed as your appetite and meals change.
I take Mounjaro for weight loss and no diabetes medicines. Should I worry about hypos?
The risk of clinically significant low blood sugar is low in that situation, and the higher figures quoted for people on insulin or a sulphonylurea do not describe you. Feeling shaky, sweaty or light-headed on treatment is more often linked to eating very little, dehydration or low blood pressure on standing, all of which are worth raising with your prescriber. Get urgent help if symptoms are severe or you feel faint.
What are the warning signs of a hypo?
Shaking, sweating, sudden hunger, dizziness, headache, weakness or drowsiness, irritability or confusion, a fast heartbeat, difficulty concentrating and blurred vision. Some people do not get clear warning symptoms, particularly after living with diabetes for a long time.
Should I reduce my insulin while taking Mounjaro?
Do not reduce or stop insulin yourself. Rapidly reducing insulin can cause serious loss of glucose control and, in some circumstances, diabetic ketoacidosis. Your clinician may need to adjust the dose, but any adjustment needs to be planned safely.
Related guides
Sources: Mounjaro Patient Information Leaflet (eMC) • NHS tirzepatide guidance
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Sources referenced on this page
Linked from the text above:
- Mounjaro Summary of Product Characteristics (eMC), text revised 29 August 2026, section 4.8 www.medicines.org.uk
- Mounjaro Patient Information Leaflet (eMC) www.medicines.org.uk
- NHS tirzepatide guidance www.nhs.uk
Standing primary references for every Monj page:
- Mounjaro (tirzepatide) Summary of Product Characteristics and Patient Information Leaflet, electronic medicines compendium
- MHRA Drug Safety Update: GLP-1 receptor agonists
- NICE TA1026: tirzepatide for managing overweight and obesity
- General Pharmaceutical Council register of pharmacies
- MHRA Yellow Card scheme
