How is chemotherapy different in people with diabetes?

Some chemotherapy medicines, and steroids used alongside them, can raise blood glucose. Nausea, vomiting, diarrhoea or eating less can instead make glucose fall or make usual diabetes medicines harder to take safely. Illness can also change glucose levels even when food intake seems unchanged.

Your oncology and diabetes teams may coordinate the treatment schedule, glucose targets and medicines. They can consider kidney function, heart health, other medicines and whether you use insulin or tablets. Diabetes does not automatically rule out chemotherapy, but it makes a personalised plan especially useful.

Bring an up-to-date list of diabetes medicines, glucose readings and supplies to the oncology appointment. Ask how often to check glucose on treatment days and between visits, and what to do if you cannot eat or keep fluids down. Keep a simple record of readings, food, symptoms and medicines so changes can be recognised.

Do not change insulin or other diabetes treatment on your own. Plan easy-to-tolerate meals and fluids if your team approves them, and tell the team before treatment if glucose has been unusually high or low.

Contact your oncology team promptly for repeated very high or low readings, confusion, unusual sleepiness, persistent vomiting, inability to drink, fever or chills. Seek emergency help for severe breathing difficulty, fainting, a seizure or sudden deterioration. Your team can give you a personal sick-day plan because thresholds and actions depend on your medicines and overall health.

Ask which chemotherapy or supporting medicines may affect glucose, whether your diabetes medicines need temporary changes, and who to call outside clinic hours. You can also ask how kidney tests, eating problems and infection symptoms will affect the next treatment decision.