Do steroids raise blood sugar?

Why the effect is so large

Corticosteroids are synthetic versions of cortisol, and raising blood glucose is part of what cortisol does. They prompt the liver to produce more glucose, reduce glucose uptake by muscle and fat, and directly impair insulin action.

The result is steroid-induced hyperglycemia, which is common enough to be expected rather than surprising. It can occur in people with no diabetes at all, and in people with well-controlled diabetes it can push readings up dramatically.

The pattern to expect

Oral steroids taken in the morning characteristically produce a pronounced afternoon and evening rise, with fasting readings less affected. That trips people up: the morning number looks acceptable while the rest of the day is well above range.

Injected steroids — for a knee, shoulder or the spine — are the ones that catch people out most. They are administered once, feel like a discrete event, and then affect glucose for days to several weeks depending on the preparation.

Which ones

• Prednisone / prednisolone — the most common oral culprit
• Dexamethasone — more potent and longer acting
• Hydrocortisone
• Triamcinolone and methylprednisolone injections
• High-dose inhaled steroids — a much smaller effect, but not zero

What to do

Do not stop a prescribed steroid because of your glucose. Steroids are prescribed for conditions that matter, and stopping suddenly after more than a short course can be genuinely dangerous. This is a conversation, not a self-adjustment.

Instead:

• Ask before you start, if you have diabetes or prediabetes: how much should I expect this to raise my glucose, and should my medication change while I am on it?
• Test more often during the course, particularly in the afternoon and evening
• Expect insulin requirements to rise, sometimes substantially, and to need to come back down as the steroid wears off — that taper matters, because staying on the higher dose risks hypos
• Mention it every time you see a clinician about your glucose

Other medications that do this

Steroids are the largest effect, but not the only one: thiazide diuretics, some atypical antipsychotics (olanzapine, clozapine in particular), immunosuppressants such as tacrolimus and ciclosporin, high-dose niacin, and decongestants containing pseudoephedrine.

If your numbers changed shortly after a new prescription, that timing is worth mentioning rather than dismissing.