Diabetes During Cancer Treatment

Cancer treatment frequently includes glucocorticoids — steroids such as prednisolone or dexamethasone — and these raise blood sugar substantially. It is one of the most predictable and least prepared-for problems in diabetes care.

The numbers are not marginal. Across studies, 32.3% of people treated with glucocorticoids develop hyperglycaemia, and 18.6% develop steroid-induced diabetes. The risk of developing diabetes is close to doubled.

The pattern to expect

Steroid-driven highs have a characteristic shape. A morning steroid dose typically produces a rise in the early afternoon, which is why a fasting reading can look reassuring while the afternoon is far out of range. Testing two hours after a meal, or in the afternoon, catches what a morning test misses.

Risk is higher with larger doses and longer courses, and in people who are older, have a higher BMI, a raised baseline HbA1c, a family history of diabetes, or a history of gestational diabetes.

What to do

• Say you have diabetes before treatment starts, and ask specifically how steroids will affect it and who will manage that.
• Test more often, and at the right time of day — afternoon and post-meal, not only fasting.
• Expect doses to change, sometimes considerably, and to change again as steroids taper.
• Do not manage this alone. High glucose during cancer treatment affects infection risk and treatment tolerance, so it is part of the cancer care, not a side issue.

And afterwards: for many people the glucose settles when the steroids stop, but up to a third of those who develop steroid-induced diabetes still have diabetes afterwards — which suggests the steroids revealed a susceptibility rather than creating one. Ask for follow-up testing rather than assuming it has resolved.