If you are sick, for example, because of an infection with a fever, a lot of things happen to your blood sugar. Hormones are released (cortisol and glucagon) that increase your blood sugar level. This will require more insulin. This is especially noticeable if you don't feel like eating. You barely eat anything and yet your blood sugar stays high. You therefore also need insulin if you are sick.

But if you have stomach flu, including vomiting and diarrhoea, you will sometimes need less insulin because glucose is lost.
Being sick, having a fever, not eating and estimating how much insulin you need is very difficult. You must learn to cope with this. Your diabetes team can inform you about this. Also, if you are sick and you have questions, contact your diabetes team so you can avoid more serious problems and difficulties.

Interpreting nausea and vomiting is sometimes difficult. It is not always clear why you are sick and must vomit. Sick children are often nauseous and vomit easily, not only with stomach flu but also for a urinary tract infection, for example.
But nausea and vomiting can also be a sign of a deficiency of insulin. It is, therefore, important to determine your blood sugar level and ketones. If your blood sugar level is high and there are ketones in your urine or blood, there will be a deficit of insulin and the nausea is caused by the high blood sugar level and ketones. If your blood sugar Is low, then you are probably sick because of the infection itself. Meanwhile you can also have ketones in your blood or urine because you have eaten not enough.

Ketones are waste products that are released when the body has a deficit of glucose and gains energy in a different way. The shortage of glucose can occur because you do not eat enough and therefore you do not ingest enough glucose or because you have too little insulin to get the glucose into the cells.