In the case of a person with diabetes, a sudden illness – especially if it includes fever, vomiting and diarrhoea – must always be taken seriously.
Inflammatory diseases increase the release of stress hormones and need for insulin. The body of a healthy person creates more insulin, while the blood sugar level remains normal. In a person with diabetes, the result is higher blood sugar. A shortage of insulin or carbohydrates may also result in higher ketone or acid levels.
See below for general instructions on sick days. Do not hesitate to contact your care povider if you are at all unsure of what you should do.
For fever, vomiting or diarrhoea, it is important to drink plenty of fluids. High blood sugar increases the excretion of urine, fever results in sweating, and your system becomes dehydrated. To prevent dehydration during illness, an adult should drink a minimum of 2–3 litres of fluids, such as mineral water, diluted fruit juice, berry soup or broth.
It is also important to consume carbohydrates, even if you have no appetite or if you are vomiting. During illness, you should consume at least 150 g of carbohydrates in some form. You may find that you have more appetite for liquid foods, such as berry soup, yoghurt, ice cream, soft drinks or juices.
Blood sugar is self-monitored more frequently than usual. In insulin-dependent diabetes, glucose sensing is utilized and/or blood sugar is measured every 2–4 hours. In other types of diabetes, blood sugar is measured as needed, for example, every 4 hours while awake. These measurements are used to assess the need for additional medication.
On sick days, the target level for blood sugar self-measurements is 8–10 mmol/l. If blood sugar exceeds 10 mmol/l, additional insulin is taken according to individual instructions in insulin therapy.
In cases of insulin-dependent diabetes, it is also advisable to check blood ketones if blood sugar is repeatedly over 14 mmol/l. If medication that removes sugar (SGLT2 inhibitors) is also used in addition to insulin therapy, it is advisable to measure ketones if blood sugar is consistently over 10 mmol/l on sick days.
From the tablet medications, metformin and SGLT2 inhibitors are paused during more severe fever illness, diarrheal and vomiting illness, or an illness that weakens the overall condition.
Each person using insulin should have individual instructions for dosing additional insulin during sick days. During febrile and inflammatory diseases, the need for insulin can even double. In cases of vomiting and diarrheal diseases, the absorption of carbohydrates may decrease. Mealtime insulin is injected according to blood sugar and carbohydrates, for example, every 4 hours. Basal insulin must always be injected even if the amount of food consumed decreases. The dose can be reduced by 20-30% if necessary, if the blood sugar tends to decrease. It is worth noting that the effect of reducing the dose of some basal insulins (such as glargine 300 units/ml and degludec insulin) is delayed, only becoming apparent after several days.
If you are unsure about how to adjust your insulin doses on sick days, contact your care provider.
If your general condition deteriorates or if no food or drink stays down.
If your blood sugar does not improve despite administering extra insulin.
If you have insulin-treated diabetes and ketone levels are above 3 mmol/l or above 1.5 mmol/l and you general condition is poor.
For fever, vomiting or diarrhoea, it is important to drink plenty of fluids. High blood sugar increases the excretion of urine, fever results in sweating, and your system becomes dehydrated. To prevent dehydration during illness, an adult should drink a minimum of 2–3 litres of fluids, such as mineral water, diluted fruit juice, berry soup or broth.
It is also important to consume carbohydrates, even if you have no appetite or if you are vomiting. During illness, you should consume at least 150 g of carbohydrates in some form. You may find that you have more appetite for liquid foods, such as berry soup, yoghurt, ice cream, soft drinks or juices.
Blood sugar is self-monitored more frequently than usual. In insulin-dependent diabetes, glucose sensing is utilized and/or blood sugar is measured every 2–4 hours. In other types of diabetes, blood sugar is measured as needed, for example, every 4 hours while awake. These measurements are used to assess the need for additional medication.
On sick days, the target level for blood sugar self-measurements is 8–10 mmol/l. If blood sugar exceeds 10 mmol/l, additional insulin is taken according to individual instructions in insulin therapy.
In cases of insulin-dependent diabetes, it is also advisable to check blood ketones if blood sugar is repeatedly over 14 mmol/l. If medication that removes sugar (SGLT2 inhibitors) is also used in addition to insulin therapy, it is advisable to measure ketones if blood sugar is consistently over 10 mmol/l on sick days.
From the tablet medications, metformin and SGLT2 inhibitors are paused during more severe fever illness, diarrheal and vomiting illness, or an illness that weakens the overall condition.
Each person using insulin should have individual instructions for dosing additional insulin during sick days. During febrile and inflammatory diseases, the need for insulin can even double. In cases of vomiting and diarrheal diseases, the absorption of carbohydrates may decrease. Mealtime insulin is injected according to blood sugar and carbohydrates, for example, every 4 hours. Basal insulin must always be injected even if the amount of food consumed decreases. The dose can be reduced by 20-30% if necessary, if the blood sugar tends to decrease. It is worth noting that the effect of reducing the dose of some basal insulins (such as glargine 300 units/ml and degludec insulin) is delayed, only becoming apparent after several days.
If you are unsure about how to adjust your insulin doses on sick days, contact your care provider.
If your general condition deteriorates or if no food or drink stays down.
If your blood sugar does not improve despite administering extra insulin.
If you have insulin-treated diabetes and ketone levels are above 3 mmol/l or above 1.5 mmol/l and you general condition is poor.
Updated 7.3.2025
