Medicines that raise blood sugar, and why steroids stand out

Some medicines push blood sugar up, usually by making insulin work less well. This page lists the common ones and explains why steroids deserve special attention. None of these is a reason to refuse a medicine you need — they are reasons to expect the change, and to ask what to do about it before you start.

The common ones

Some antipsychotics. Olanzapine and quetiapine especially. They reduce how well insulin works.

Thiazide diuretics. Hydrochlorothiazide and its relatives, commonly prescribed for blood pressure.

Decongestants. Pseudoephedrine, sold over the counter in cold and sinus products. It often hides inside combination products, so it is worth reading the ingredient list.

Beta blockers. They push glucose up a little — but they also hide lows, which matters more. That is covered on the page about medicines that lower blood sugar or hide a low.

Hormonal contraceptives. These can shift how your body handles glucose. It is worth watching your numbers closely for the first few cycles.

Some HIV medicines. Protease inhibitors in particular are linked to higher glucose.

Transplant medicines. Tacrolimus and cyclosporine raise glucose, and they are usually non-negotiable. The plan is to adjust insulin around them.

Please don't read this list as a set of medicines to avoid. People do stop needed medication after reading lists like this one, and that is a worse outcome than a week of higher numbers. The better move is to ask, at the moment of prescribing: "Will this raise my blood sugar, and what should I do about my insulin?"

Steroids deserve their own section

A short course of prednisone for a chest infection, or one cortisone shot in a knee, can double how much insulin you need for days. Most people are never told.

Prednisone, once each morning

The rise begins around four hours after the dose and can run for twelve. The classic pattern is a normal morning, a high afternoon and evening, and a better dawn. Knowing that shape helps you and your team plan where the extra insulin goes.

Dexamethasone

Dexamethasone works for twelve to thirty-six hours, so it covers the night too. There is no quiet window in the day where its effect drops away.

The injection counts

A joint, spine or skin injection is a steroid dose. People often don't report it because it didn't come in a bottle — but it can raise your glucose just the same. Say "I have type 1 diabetes" at the moment any steroid is offered, including by a physiotherapist or a surgeon.

Call your team when it's prescribed

Call your diabetes team when a steroid is prescribed — not three high days later. Adjusting insulin for a steroid course is a planned change, and diabetes teams do it all the time. Calling early means you get a plan for the rise and for the taper, rather than chasing numbers after they have already climbed.