Tresiba Drug Interactions: What to Avoid and What to Tell Your Doctor

Tresiba (insulin degludec) is an insulin — which means it works by lowering blood sugar. Many other medications can make Tresiba more or less effective, or amplify its blood-sugar-lowering effect to dangerous levels. Understanding these interactions is essential to using Tresiba safely.

This guide covers the most clinically important drug interactions with Tresiba — what they are, what happens, and what you should tell your doctor.

Drugs That Increase Tresiba's Blood-Lowering Effect (Hypoglycemia Risk)

These medications can make Tresiba work "harder" than expected, increasing the risk of dangerously low blood sugar:

Other diabetes medications (sulfonylureas, GLP-1 agonists, meglitinides): Combining Tresiba with other blood-sugar-lowering drugs increases hypoglycemia risk. Your doctor may need to adjust your Tresiba dose when starting, stopping, or changing the dose of any other diabetes medication.

ACE inhibitors and ARBs (e.g., lisinopril, enalapril, losartan, valsartan): Blood pressure medications in these classes can increase the glucose-lowering effect of insulin. Monitor blood sugar more carefully when starting or stopping these medications.

MAO inhibitors: Monoamine oxidase inhibitors (used for depression or Parkinson's disease) can significantly increase the blood-sugar-lowering effect of insulin. Careful monitoring is required.

High-dose salicylates (aspirin): Aspirin in high doses (3 grams or more per day) can increase insulin's blood-sugar-lowering effect and raise hypoglycemia risk.

Fluoxetine (Prozac): This antidepressant can increase the blood-sugar-lowering effect of insulin. Monitor blood sugar carefully if you start or stop fluoxetine.

Drugs That Decrease Tresiba's Effectiveness (Hyperglycemia Risk)

These medications can make Tresiba work less effectively, causing blood sugar to rise higher than expected:

Corticosteroids (e.g., prednisone, dexamethasone, methylprednisolone): Steroids raise blood sugar significantly. If you're prescribed steroids, you may need to temporarily increase your Tresiba dose. Work closely with your doctor when starting or stopping steroid treatment.

Thiazide diuretics (e.g., hydrochlorothiazide, chlorothiazide): Water pills in the thiazide class can raise blood sugar. Your insulin dose may need adjustment.

Atypical antipsychotics (e.g., olanzapine/Zyprexa, clozapine, aripiprazole/Abilify): These psychiatric medications are associated with hyperglycemia and can reduce insulin effectiveness. Careful monitoring and possible dose adjustments are needed.

Thyroid hormones: Thyroid hormone medications can reduce insulin sensitivity. Monitor blood sugar when thyroid medication doses are adjusted.

Sympathomimetics (e.g., albuterol/Ventolin, epinephrine, pseudoephedrine): Bronchodilators and decongestants can raise blood sugar and may reduce Tresiba's effectiveness.

Niacin (vitamin B3) at high doses: High-dose niacin (used for cholesterol) can increase blood sugar and may reduce insulin's effect.

Drugs with Variable Effects (Can Raise OR Lower Blood Sugar)

Beta-blockers (e.g., metoprolol/Lopressor, atenolol/Tenormin, propranolol/Inderal): These heart and blood pressure medications can both raise AND lower blood sugar — and, more importantly, they can mask the warning signs of hypoglycemia (like rapid heartbeat and shakiness). If you take a beta-blocker, you may not feel low blood sugar coming until it's severe. Monitor blood sugar closely.

Alcohol: Alcohol can either increase or decrease blood sugar. It also interferes with the body's ability to recover from hypoglycemia by blocking liver glucose release. Avoid alcohol while using Tresiba or drink very cautiously and monitor blood sugar closely.

Clonidine: This blood pressure medication has unpredictable effects on blood sugar and can also mask hypoglycemia symptoms.

Special Warning: Thiazolidinediones (TZDs) and Heart Failure

Pioglitazone (Actos) and rosiglitazone belong to a class called TZDs. Taking these with any insulin, including Tresiba, can cause or worsen heart failure — even in patients who have never had heart problems. Contact your doctor immediately if you develop new or worsening shortness of breath, sudden weight gain, or swelling in your ankles or feet.

What to Tell Your Doctor Before Starting Tresiba

Before starting Tresiba, tell your healthcare provider about ALL medications you take — prescription, over-the-counter, vitamins, supplements, and herbal products. Pay particular attention to:

All other diabetes medications (oral or injectable)

Blood pressure medications (especially beta-blockers, ACE inhibitors, and ARBs)

Corticosteroids (prednisone, inhaled steroids, steroid joint injections)

Psychiatric medications (antipsychotics, antidepressants, lithium)

Cholesterol medications (especially high-dose niacin)

For a complete guide to side effects, see: Tresiba Side Effects: What to Expect and When to Call Your Doctor.

If you're having trouble finding Tresiba at your pharmacy, medfinder can help you locate it quickly.