Vomiting in people with type 2 diabetes can signal anything from a minor stomach upset to a life-threatening complication. Whilst gastroenteritis and medication side effects are common causes, serious conditions such as diabetic ketoacidosis, hyperosmolar hyperglycaemic state, and gastroparesis require prompt recognition and treatment. Understanding when vomiting represents a medical emergency, how to manage blood glucose levels during illness, and which diabetes medications to adjust can prevent dangerous complications. This guide explains the causes of type 2 diabetes vomiting, outlines UK sick day rules, and clarifies when to seek urgent medical attention.

Why Does Type 2 Diabetes Cause Vomiting?

Vomiting in people with type 2 diabetes can arise from several diabetes-related and unrelated causes. Understanding the underlying mechanisms helps distinguish between routine illness and serious complications requiring urgent attention.

Diabetic ketoacidosis (DKA), though more common in type 1 diabetes, can occasionally occur in type 2 diabetes, particularly during severe illness, stress, or in people taking SGLT2 inhibitors. When insulin levels are insufficient, the body breaks down fat for energy, producing ketones that accumulate in the blood. This metabolic acidosis triggers nausea and vomiting, alongside abdominal pain, rapid breathing, and a characteristic fruity breath odour. DKA represents a medical emergency requiring immediate hospital treatment. Blood ketone testing is preferred over urine testing, especially for those taking SGLT2 inhibitors, as it provides more accurate and timely results.

Gastroparesis is a chronic complication that can occur in people with longstanding diabetes. High blood glucose levels over time can damage the vagus nerve, which controls stomach emptying. This autonomic neuropathy causes delayed gastric emptying, leading to nausea, vomiting (often of undigested food), early satiety, and bloating. Symptoms typically worsen after meals, particularly those high in fat or fibre. The prevalence varies depending on diagnostic criteria and is more common in type 1 than type 2 diabetes.

Hyperosmolar hyperglycaemic state (HHS) is a serious complication specific to type 2 diabetes, characterised by extremely high blood glucose levels (often above 30 mmol/L) without significant ketone production. Severe dehydration develops, and nausea with vomiting may occur alongside confusion, drowsiness, and increased thirst. HHS develops gradually over days to weeks and requires emergency medical intervention.

Pancreatitis should be considered as an important cause of vomiting, particularly in people taking GLP-1 receptor agonists or those with gallstones or hypertriglyceridaemia. Severe epigastric pain radiating to the back, alongside persistent vomiting, warrants urgent medical assessment.

Certain diabetes medications can cause gastrointestinal side effects. Metformin commonly causes nausea, particularly when first started or if the dose is increased too quickly. GLP-1 receptor agonists (such as semaglutide or dulaglutide) slow gastric emptying as part of their mechanism of action, which can lead to nausea and vomiting in some patients. These agents may worsen symptoms in people with existing gastroparesis and should be used with caution or avoided in confirmed cases. SGLT2 inhibitors have been associated with a rare but important risk of diabetic ketoacidosis, even with near-normal blood glucose levels (euglycaemic DKA). The MHRA advises that blood ketone testing is preferred in people taking SGLT2 inhibitors, as this complication requires urgent recognition and treatment even when glucose readings appear reassuring.

Other causes of vomiting unrelated to diabetes—such as gastroenteritis, bowel obstruction, myocardial infarction, or medication side effects—should also be considered and may require separate investigation.

When Vomiting in Type 2 Diabetes Is a Medical Emergency

Recognising when vomiting requires urgent medical attention is crucial for preventing serious complications and potentially life-threatening situations in people with type 2 diabetes.

Seek immediate emergency care (call 999 or attend A&E) if vomiting is accompanied by:

• Signs of diabetic ketoacidosis: deep, rapid breathing (Kussmaul respiration), fruity-smelling breath, severe abdominal pain, confusion, or drowsiness. Check blood glucose and ketones if possible—blood glucose typically exceeds 11 mmol/L and blood ketones are above 3 mmol/L or urine ketones show 2+ or more. Blood ketone testing is preferred, particularly for people taking SGLT2 inhibitors.

• Symptoms of hyperosmolar hyperglycaemic state: extreme thirst, very high blood glucose readings (often above 30 mmol/L), confusion, visual disturbances, weakness on one side of the body, or seizures. HHS can mimic stroke and requires urgent hospital treatment with intravenous fluids and insulin.

• Severe dehydration indicators: inability to keep down any fluids for more than 6 hours, reduced urine output or dark concentrated urine, dizziness when standing, rapid heartbeat, sunken eyes, or extreme weakness.

• Persistent hypoglycaemia: blood glucose below 4 mmol/L that doesn't respond to usual treatment, particularly if you're unable to keep down oral glucose or food. This is especially concerning for those taking insulin or sulphonylureas.

• Signs of serious infection or other acute illness: high fever (above 38°C), severe abdominal pain (particularly if radiating to the back, which may suggest pancreatitis), blood in vomit, chest pain, or symptoms suggesting serious infection such as urinary tract infection or pneumonia, which can rapidly destabilise diabetes control.

• Pregnancy: if you are pregnant and have diabetes with vomiting or feel unwell, seek urgent same-day medical assessment.

The MHRA advises that people taking SGLT2 inhibitors who develop persistent vomiting should stop the medication immediately and seek medical advice promptly due to the risk of euglycaemic ketoacidosis. Even with normal or slightly elevated blood glucose, ketone levels may be dangerously high, requiring specific testing and treatment. Blood ketone testing is preferred in this situation, as urine ketones may be misleading.

If you are unsure whether your symptoms require emergency care, contact NHS 111 for urgent advice. They can guide you on the most appropriate next steps and arrange timely assessment if needed.

Managing Blood Sugar Levels During Vomiting Episodes

Maintaining glycaemic control during illness with vomiting presents unique challenges, but following UK sick day rules can prevent dangerous fluctuations in blood glucose levels.

Adjust diabetes medications according to sick day rules (SADMAN). Illness and stress typically raise blood glucose levels through counter-regulatory hormones like cortisol and adrenaline, but some medications must be temporarily stopped during vomiting or dehydration:

• Stop SGLT2 inhibitors (such as dapagliflozin, empagliflozin, canagliflozin) immediately if you are vomiting or dehydrated, due to the risk of diabetic ketoacidosis. Do not restart until you have recovered, are eating and drinking normally, ketones are negative, and you have discussed this with your healthcare team (typically 24–48 hours after recovery).

• Stop metformin during vomiting or dehydration, as continued use may increase the risk of lactic acidosis. Restart once you are eating and drinking normally, typically after 24–48 hours.

• Reduce or withhold sulphonylureas (such as gliclazide) if you are unable to maintain your usual carbohydrate intake, to reduce the risk of hypoglycaemia. Seek advice from your GP or diabetes team.

• Continue insulin—do not stop your basal (background) insulin. You may need to adjust doses based on blood glucose readings and ketone levels, but never stop insulin completely without medical guidance. If in doubt, contact your diabetes specialist nurse or GP for advice on dose adjustments.

• Continue other diabetes medications unless advised otherwise by your healthcare team.

Monitor blood glucose more frequently—ideally every 2–4 hours during illness. Keep a written record of readings, as patterns help guide treatment decisions. Check blood ketones if blood glucose exceeds 13–14 mmol/L, if you feel unwell, or if you are taking an SGLT2 inhibitor (check ketones even if blood glucose is normal or only slightly raised). Blood ketone testing is preferred over urine testing, especially for people on SGLT2 inhibitors. Blood ketone levels above 1.5 mmol/L require medical advice, whilst levels above 3 mmol/L indicate DKA requiring emergency treatment. Urine ketone testing strips are an alternative if blood ketone testing isn't available.

Maintain hydration by sipping small amounts of fluid frequently—aim for at least 100 ml every 15–20 minutes. If blood glucose is elevated (above 10 mmol/L), choose sugar-free fluids like water, sugar-free squash, or clear broth. If blood glucose is normal or low (below 7 mmol/L), alternate between sugar-free and sugar-containing drinks such as diluted fruit juice, flat lemonade, or oral rehydration solutions (available from pharmacies). If you have chronic kidney disease or heart failure, seek tailored advice from your clinician on appropriate fluid targets, as your needs may differ.

Attempt to consume carbohydrates even if you cannot manage regular meals. Suitable options during vomiting include small sips of milk, ice lollies, jelly, smooth soup, or plain crackers. Aim for approximately 10–15 grams of carbohydrate every hour to prevent hypoglycaemia whilst avoiding large meals that may worsen nausea. The NHS recommends having a sick day box prepared containing appropriate foods, drinks, a thermometer, and testing supplies.

If you are struggling to manage at home or are unsure what to do, contact your diabetes specialist nurse, GP, or NHS 111 for urgent advice.

Treatment Options for Diabetes-Related Nausea and Vomiting

Treatment approaches depend on the underlying cause, ranging from medication adjustments to specific therapies for diabetes complications.

For medication-related nausea, particularly with metformin or GLP-1 receptor agonists, several strategies can help. Taking metformin with or immediately after meals and using modified-release formulations reduces gastrointestinal side effects. If starting a GLP-1 agonist, gradual dose titration as per the manufacturer's schedule minimises nausea. Eating smaller, more frequent meals and avoiding high-fat foods can also help. If symptoms persist despite these measures, your GP or diabetes specialist may consider alternative medications or dose adjustments. GLP-1 receptor agonists should be used with caution or avoided in people with suspected or confirmed gastroparesis, as they may worsen gastric emptying.

Gastroparesis management requires a multifaceted approach and specialist input. If gastroparesis is suspected, your GP should arrange investigation to exclude mechanical obstruction (such as upper gastrointestinal endoscopy) and may refer you to a gastroenterologist for further assessment, which may include gastric emptying studies.

Dietary modifications form the cornerstone of treatment: eating smaller, more frequent meals (5–6 per day), reducing dietary fat and fibre, choosing well-cooked vegetables, and avoiding carbonated drinks can significantly improve symptoms. Liquid or pureed meals may be better tolerated during flare-ups.

Prokinetic medications such as metoclopramide or domperidone enhance gastric motility and may be prescribed for moderate to severe symptoms, typically under specialist guidance. These medicines are largely used off-label for gastroparesis and require careful monitoring:

• Metoclopramide is limited to short courses (maximum 5 days in adults) due to the risk of neurological side effects, including extrapyramidal symptoms and tardive dyskinesia. It is contraindicated in Parkinson's disease. Chronic or recurrent symptoms should be managed under specialist supervision.

• Domperidone is restricted by the MHRA due to the risk of serious cardiac side effects, including QT interval prolongation and arrhythmias. The maximum dose is 10 mg three times daily, and it should be used for the shortest possible duration. It is contraindicated in people with significant cardiac disease, QT prolongation, or those taking potent CYP3A4 inhibitors. An ECG may be required before starting treatment if cardiac risk factors are present.

• Erythromycin may be used as a short-term prokinetic under specialist care, but tachyphylaxis (reduced effectiveness over time) and QT prolongation risk limit its use.

Antiemetic medications provide symptomatic relief for nausea and vomiting. Options include ondansetron (a 5-HT3 antagonist), prochlorperazine, or cyclizine, prescribed based on individual circumstances and potential drug interactions. Ondansetron can prolong the QT interval and may cause constipation; your doctor will check for interactions and cardiac risk factors. NICE guidance suggests considering antiemetics alongside treatment of the underlying cause.

Optimising glycaemic control is fundamental, as improved blood glucose levels can reduce gastroparesis symptoms and prevent DKA or HHS. This may involve intensifying diabetes treatment, switching medication classes, or initiating insulin therapy. For severe gastroparesis unresponsive to medical management, specialist referral for consideration of gastric electrical stimulation or other interventions may be appropriate, though these remain relatively uncommon treatments in the UK.

If you experience side effects from any medication, you can report them via the MHRA Yellow Card Scheme at yellowcard.mhra.gov.uk or through the Yellow Card app. Reporting helps improve the safety of medicines for everyone.

When to Contact Your GP or Diabetes Care Team

Knowing when to seek non-emergency medical advice helps prevent complications whilst avoiding unnecessary hospital attendance.

Contact your GP or diabetes specialist nurse within 24 hours if:

• Vomiting persists for more than 24 hours, even if you can keep down some fluids

• Blood glucose levels remain consistently above 15 mmol/L despite taking your usual medications

• Blood ketones are between 1.5–3.0 mmol/L or urine ketones show 2+

• You're unable to eat solid food for more than 24 hours

• You have signs of dehydration (reduced urine output, dizziness, dry mouth) but can still drink fluids

• You develop symptoms of a urinary tract infection (burning on urination, frequency, lower abdominal pain) or other infection

• You're uncertain about medication adjustments during illness

• You are pregnant and have diabetes with vomiting or feel unwell

Schedule a routine appointment if:

• You experience recurrent episodes of nausea or vomiting, particularly after meals, which may indicate gastroparesis requiring investigation and specialist referral

• Medication side effects are affecting your quality of life or adherence to treatment

• You need advice about sick day rules or would like to develop a personalised sick day action plan

• You're experiencing frequent episodes of poor glycaemic control that may benefit from treatment review

Diabetes specialist nurses often provide telephone advice services and can guide you through sick day management, medication adjustments, and when to escalate care. Many diabetes centres offer direct access to specialist advice, which can be invaluable during acute illness.

If you are unsure or cannot reach your usual healthcare team, contact NHS 111 for urgent advice. They are available 24 hours a day and can help you decide on the most appropriate course of action.

Preventive measures include attending annual diabetes reviews, maintaining good overall glycaemic control, and ensuring you have an up-to-date sick day action plan. NICE recommends individualised HbA1c targets: typically 48 mmol/mol for most adults with type 2 diabetes managed without medications associated with hypoglycaemia, or 53 mmol/mol for those on insulin or sulphonylureas, though targets should be tailored to individual circumstances. The NHS advises keeping emergency contact numbers readily available and ensuring family members know the signs of serious diabetes complications requiring urgent medical attention.

Frequently Asked Questions