Diabetes Sick-Day Rules: Managing Blood Sugar During Fever, Vomiting and Illness
Illness can make diabetes harder to manage. Fever, infection, vomiting, diarrhoea and reduced food intake can change blood glucose levels and increase the risk of dehydration. Having a written sick-day plan helps you know what to monitor, when medicines may need temporary review and when to seek urgent medical care.
Why can blood glucose change during illness?
When the body is fighting an infection or dealing with physical stress, hormones can raise blood glucose even if you are eating less than usual. On the other hand, vomiting, diarrhoea or missed meals can increase the risk of low blood glucose in people using insulin or certain glucose-lowering medicines. Dehydration can further complicate glucose control and kidney function.
What should you do when you are unwell?
- Monitor glucose more often. Follow the frequency advised in your personal sick-day plan. People with Type 1 Diabetes may also need ketone checks, particularly when glucose is high or they feel unwell.
- Drink fluids regularly. Take small, frequent sips if nausea is present. Follow your clinician’s advice if you have heart failure, kidney disease or a prescribed fluid restriction.
- Try to maintain nutrition. If you cannot eat your usual meals, use an individualized plan for fluids and carbohydrate intake. Do not force food if you are repeatedly vomiting.
- Keep a record. Note glucose readings, temperature, symptoms, fluids, food intake and medicines taken.
- Know whom to contact. Keep your diabetes team’s contact details and understand when to seek urgent care.
Should diabetes medicines be stopped during sick days?
Do not stop or change every diabetes medicine automatically. The right plan depends on the medicine, glucose readings, hydration, kidney function and severity of illness. Some medicines may need temporary withholding during significant dehydration, vomiting, diarrhoea or inability to eat and drink normally; others, particularly insulin in Type 1 Diabetes, must not be stopped without specific medical direction.
Insulin
People with Type 1 Diabetes generally need basal insulin even when they are not eating, because stopping it can lead to diabetic ketoacidosis (DKA). Insulin doses may need adjustment during illness, but changes should follow a clinician-provided plan. People with Type 2 Diabetes who use insulin should also follow their individualized instructions and monitor for hypoglycaemia if intake falls.
SGLT2 inhibitors
SGLT2 inhibitors may need to be temporarily withheld during significant acute illness, dehydration, prolonged fasting or surgery because of the risk of ketoacidosis, which can sometimes occur without very high glucose. Follow the sick-day instructions provided by your prescribing clinician and seek urgent assessment if symptoms suggest ketoacidosis.
Metformin
Metformin may need temporary review during significant dehydration, persistent vomiting or diarrhoea, severe infection, or conditions that impair kidney function. Contact your clinician for instructions rather than making long-term changes yourself.
GLP-1-based medicines
If severe or persistent gastrointestinal symptoms prevent you from maintaining fluids, contact your treating clinician for advice about the next dose and dehydration risk. Do not take extra doses or change the schedule without guidance.
When should you seek urgent medical care?
Seek urgent medical assessment if you have persistent vomiting or diarrhoea, cannot keep fluids down, have signs of significant dehydration, worsening drowsiness or confusion, rapid or difficult breathing, severe abdominal pain, or high glucose that is not improving according to your plan. If ketones are elevated or you suspect DKA, do not wait for glucose to become extremely high before seeking help.
Emergency assessment is especially important for people with Type 1 Diabetes, people taking SGLT2 inhibitors who are unwell, and anyone who is unable to maintain hydration or safely monitor their condition.
Prepare a sick-day plan before you need it
- Write down how often to check glucose and, if relevant, ketones.
- List which medicines need specific sick-day instructions.
- Keep a supply of glucose-monitoring equipment, fluids and any prescribed ketone-testing supplies.
- Know the clinician’s contact details and local emergency options.
- Review the plan after changes to medicines, kidney function or other major health conditions.
Frequently asked questions
Can fever increase blood glucose even if I eat less?
Yes. Stress hormones released during illness can raise glucose despite reduced food intake. Continue monitoring and follow your individualized sick-day plan.
Should I stop insulin if I cannot eat?
Never stop basal insulin in Type 1 Diabetes unless specifically directed by a qualified clinician. You may need dose adjustments and closer monitoring; seek advice promptly if you cannot eat or drink.
Can diabetic ketoacidosis happen with glucose that is not very high?
Yes. SGLT2 inhibitors can be associated with ketoacidosis even when glucose is below the levels often expected in DKA. Symptoms such as nausea, vomiting, abdominal pain, unusual fatigue or rapid breathing require urgent medical assessment.
Key takeaway
Illness can affect glucose, hydration and medicine safety. Monitor more frequently, follow your personal medication instructions, maintain fluids when safe and seek urgent care for warning signs. A sick-day plan should be made with your diabetes clinician in advance—not improvised during a severe illness.
Related diabetes resources
- Complete Diabetes Guide: Symptoms, Tests and Treatment
- Diabetes Specialist in Ahmedabad
- Diabetes and Kidney Protection
- SGLT2 Inhibitors in Diabetes
Medical disclaimer: This article is for general education and does not replace an individualized sick-day plan. Medicine instructions vary by patient and medication. Seek urgent medical care for severe symptoms.
Dr. Moxit Shah, DM Endocrinology
Vishuddha Diabetes, Thyroid, Weight Loss Clinic
104-105, Elite Magnum, Bhuyangdev Cross Road, Opp. Utsav Elegance, Vardhmannagar Society, Ghatlodiya/Memnagar, Ahmedabad, Gujarat 380061
Phone: +91 99799 92797
