What each document reports
All three regulators use the same threshold for a clinically important low: plasma glucose under 54 mg/dL, which Canada writes as 3.0 mmol/L. [1][3][4] The figures come mainly from SURMOUNT-2, the 72-week Zepbound® trial in adults with type 2 diabetes. [1]
| Source and population | Zepbound® or tirzepatide | Comparison |
|---|---|---|
| US label: SURMOUNT-2, type 2 diabetes, below 54 mg/dL [1] | 4.2% | Placebo 1.3% |
| US label: SURMOUNT-2, Zepbound® with a sulfonylurea [1] | 10.3% | Zepbound® without one 2.1% |
| US label: SURMOUNT-1, no diabetes, not systematically collected [1] | 0.3% | Placebo 0% |
| Canada: SURMOUNT-2, below 3.0 mmol/L [3] | 4.2% (10.3% with a sulfonylurea) | Placebo 1.3% |
| EU, tirzepatide weight trial in type 2 diabetes [4] | 4.2%; no severe episodes | Placebo 1.3% |
Inside SURMOUNT-2
SURMOUNT-2 enrolled 938 adults with a BMI of 27 or more and type 2 diabetes with an HbA1c of 7% to 10%. They were managed with diet and exercise or with diabetes tablets, but not DPP-4 inhibitors or GLP-1 receptor agonists; people using insulin or injectable GLP-1 medicines were excluded. [1][5] The trial was funded by Eli Lilly, and its published report described the most frequent adverse events as stomach-related and mostly mild to moderate. [5]
Blood sugar control changed a lot. Average HbA1c started at 8.0% and fell by 2.1 points on both Zepbound® doses, against 0.5 on placebo. [1] Without a sulfonylurea, 2.1% of people on Zepbound® had a reading below 54 mg/dL; with one, the figure rose to 10.3%. [1] The label adds that tirzepatide with insulin also increases the risk, a statement drawn from beyond this trial since insulin users were not enrolled. [1]
Without diabetes: thin data, one clear sentence
Most people take Zepbound® without diabetes. SURMOUNT-1 did not collect low blood sugar systematically; the 0.3% figure is a count of readings that happened to be recorded. [1] Canada says the same and gives no rate. [3] The two sleep apnea trials excluded people with type 2 diabetes and report nothing separate. [1] Even so, section 5.7 states that hypoglycemia has been associated with Zepbound® and with GLP-1 receptor agonists in adults without type 2 diabetes. [1]
A published case report gives an example rather than a rate: six days after a first tirzepatide injection, a non-diabetic woman with obesity reached the emergency department vomiting persistently; her blood tests showed ketoacidosis alongside a mildly low glucose, and she was well again within two days. [9] One patient cannot tell us how often this happens or whether the medicine caused it.
A post hoc analysis of SURMOUNT-1 and -2, written largely by Lilly authors, grouped people by whether they lost at least 5% of their weight by week 8 and listed hypoglycaemia among the outcomes it assessed, but its abstract does not report a hypoglycaemia result. [6] Outside the medicine, MedlinePlus lists causes of low blood sugar in people without diabetes: alcohol, a rare insulin-making tumour, a lack of cortisol, growth or thyroid hormone, severe heart, kidney or liver failure, sepsis, some types of weight-loss surgery (usually years later) and certain non-diabetes medicines. [7]
Why the medicines you combine matter
- Supported by the label: Zepbound® lowers blood glucose, and tirzepatide stimulates insulin release in a glucose-dependent way. [1] The warning is therefore framed around combinations: the risk rises with a sulfonylurea or insulin, and section 7.1 asks prescribers to consider lowering those doses when Zepbound® starts. [1] Canada adds that glucose should be monitored at the start for people on a sulfonylurea or insulin. [3]
- From the European patient leaflet: low blood sugar is described as very common when tirzepatide is used with a sulfonylurea and/or insulin, and the leaflet says those doses may need lowering. [4]
- From NIDDK: the diabetes medicines that can cause lows are insulin and two types of tablet, sulfonylureas, which raise insulin over several hours, and meglitinides, taken before meals. [8]
- Proposed but not measured for Zepbound®: tirzepatide decreases calorie intake, [1] and NIDDK lists too few carbohydrates, fasting, more activity than usual, alcohol without food and being sick as triggers for people on these medicines. [8] No Zepbound® study has linked eating less to lows.
- Not for combining: the label advises against using Zepbound® with other tirzepatide products or any GLP-1 receptor agonist, and Canada names Mounjaro® and DPP-4 inhibitors as well. [1][3]
Signs to know
The Medication Guide’s list covers dizziness or light-headedness, blurred vision, anxiety, irritability or mood changes, sweating, slurred speech, hunger, confusion or drowsiness, shakiness, weakness, headache, a fast heartbeat and feeling jittery. [2] MedlinePlus notes that many people with diabetes get much the same symptoms each time, and that a low can occur without any warning symptoms, which is called hypoglycemic unawareness. [7]
NIDDK describes how a low during sleep can show: crying out or nightmares, sweat-dampened sheets, and waking tired, irritable or confused. [8] For people using Zepbound® for sleep apnea who also have diabetes, those night-time signs are worth separating from the sleep apnea itself. Canada places severe low blood sugar, with disorientation, loss of consciousness or seizure, in its table of serious side effects. [3]
Eyes, driving and planning ahead
Quick improvements in blood sugar can bring their own warning: section 5.8 reports a temporary worsening of diabetic retinopathy with rapid improvement in glucose control, so people with a history of retinopathy are monitored, and the Medication Guide asks people with type 2 diabetes to report changes in vision. [1][2]
Canada advises against driving or using machines if you have any signs of low blood sugar, because it can affect concentration, and asks that people on a sulfonylurea or insulin take precautions at the wheel. [3]
The Medication Guide asks you to talk about low blood sugar and how to handle it before starting Zepbound®, and to name any insulin or sulfonylurea you take. [2] MedlinePlus describes the kinds of treatment a provider may teach, such as a sugary drink, food, glucose tablets or glucagon, [7] and NIDDK suggests discussing a glucagon kit, teaching family or coworkers when to use it, and wearing medical ID. [8] The details of your own plan come from your clinician, not from this page.
Zepbound® and Mounjaro® are registered trademarks 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 |
|---|---|---|---|
| Someone who cannot be woken, is losing consciousness or is having a seizure | Emergency services (911 or local number); glucagon from someone trained to give it | Emergency | NIDDK [8]; MedlinePlus [7] |
| Low blood sugar signs that do not improve after a sugary snack | Emergency room or emergency services; do not drive yourself | Emergency | MedlinePlus [7] |
| An episode with disorientation or confusion, even after it has passed | Your healthcare professional, in all cases | Today | Canadian patient information [3] |
| Shakiness, sweating, hunger or a fast heartbeat while also on insulin or a sulfonylurea | Treat as your plan says, then tell your prescriber | Today | Medication Guide [2]; label §5.7 [1] |
| Vomiting or eating very little while on insulin or a sulfonylurea | Your diabetes team, for sick-day advice | Today | NIDDK [8] |
| Changes in vision with type 2 diabetes | Your healthcare provider | At your next appointment | Medication Guide [2] |
| Low blood sugar symptoms without diabetes, or a planned fast for a procedure | Your prescriber, ahead of time | At your next appointment | MedlinePlus [7]; NIDDK [8] |
