Frequent Colds, Slow Recovery and Blood Sugar
Elevated glucose measurably impairs immune function — and illness raises blood sugar in return, which is worth planning for.
Getting ill more often than you used to, or taking longer to recover, is on the list of things worth investigating rather than accepting.
How glucose affects immunity
White cell function is reduced at higher glucose levels. The cells responsible for engulfing and destroying pathogens work less effectively, and this has been demonstrated directly.
Circulation to tissues is reduced, which slows the delivery of immune cells to where they're needed.
Wound healing is slower, which is the same mechanism visible from the outside.
The practical result is infections that are both more likely and slower to clear.
The loop in the other direction
Illness raises blood sugar. Infection triggers a stress response, cortisol rises, the liver releases glucose, and insulin sensitivity falls.
So a cold can push readings up substantially even if you're eating less than usual — which confuses people who assume reduced appetite should lower them.
Sick-day planning
This is genuinely important if you have diabetes and it's frequently not discussed until it's needed.
Ask your care team for sick-day rules before you need them. These cover monitoring frequency, whether and how medication doses change, when to seek help, and what to do if you can't keep food down.
Some medications need holding during acute illness — SGLT2 inhibitors in particular, because of ketoacidosis risk when unwell or dehydrated. That's a specific instruction from your prescriber rather than something to work out during a fever.
Keep monitoring even when eating little. This is the counterintuitive part.
Fluids matter more than food during a short illness.
If you don't have a diagnosis
Recurrent infections — chest infections, urinary infections, thrush, skin infections, slow-healing wounds — appear on the list of presenting features of undiagnosed diabetes.
If you've had more than a couple this year without an obvious reason, ask for a glucose test.
What helps generally
Sleep, which affects immune function substantially.
Adequate protein, which antibody production requires.
Vaccination as recommended. Flu and pneumococcal vaccination are specifically recommended for people with diabetes for good reason.
Improving glucose control, which improves immune function over weeks.
Try this week: if you have diabetes, ask your care team for written sick-day rules before you need them.
Education, not medical advice. Illness with diabetes can change medication needs — ask your care team in advance.