Which medicines can raise blood sugar, like steroids and cough syrups?

Yes, some medicines can push sugars up. The most common ones are well known and we can plan for them.

Steroids are the biggest culprit

This includes steroid tablets (like prednisolone), injections, and sometimes even high-dose steroid inhalers or repeated local steroid injections. Steroids increase insulin resistance and can raise sugars quickly, especially after meals.^[2,6]

Practical tip:

When steroids start, sugars can rise within 24 to 72 hours. When steroids are tapered down, sugars can also come down, so doses may need readjustment.^[7]

Some psychiatric medicines can raise sugar and weight

• Certain atypical antipsychotic medicines are associated with metabolic changes, including hyperglycaemia and diabetes risk. This is clearly mentioned in regulatory safety information for this drug class.^[2]
• Not every medicine has the same risk, so your treating psychiatrist and endocrinologist can coordinate the safest option.

Some cold and “blocked nose” medicines can raise sugar

Oral decongestants such as pseudoephedrine and phenylephrine may raise blood glucose in some people, and labels often advise caution in diabetes.^[4,8]

Cough syrups and tonics may contain sugar

Many syrups are sweetened for taste, so they add extra carbohydrates without you realising. Prefer tablets when possible, or ask specifically for sugar-free cough preparations. ^[8]

What you should do when starting any of these medicines

• Tell the prescribing doctor that you have diabetes.
• Monitor sugars more often for a few days (fasting plus post-meal, or as advised).
• If sugars are repeatedly high, contact your diabetes doctor early. Temporary dose adjustment or short-term insulin is sometimes needed, especially with steroids.
• When steroids are reduced, keep monitoring. Over-treatment can cause low sugars.

Safety note:

Do not stop steroids, psychiatric medicines, or your diabetes medicines on your own. These decisions depend on your sugars, kidney function, infection severity, and other medicines. Always coordinate with your endocrinologist or treating physician.