Drug interactions
Insulin degludec / insulin aspart + Levothyroxine
Severity: Moderate
Insulin degludec / insulin aspart and Levothyroxine: moderate interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Thyroid hormone increases metabolic rate and glucose production, so starting or increasing levothyroxine can worsen glycemic control in patients with diabetes. Insulin requirements may rise, and they may fall again if thyroid hormone is reduced.
What this interaction means in plain words
Insulin degludec / insulin aspart and Levothyroxine can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Why it happens
Thyroid hormone increases gluconeogenesis, glycogenolysis and glucose turnover, opposing the glucose-lowering effect of insulin.
What to do
Monitor blood glucose more frequently when levothyroxine is started or its dose changed. Adjust the insulin dose as needed.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Levothyroxine
Frequently asked questions
Can I take Insulin degludec / insulin aspart with Levothyroxine?
MediHelp rates the interaction as moderate. Insulin degludec / insulin aspart and Levothyroxine can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Thyroid hormone increases metabolic rate and glucose production, so starting or increasing levothyroxine can worsen glycemic control in patients with diabetes. Insulin requirements may rise, and they may fall again if thyroid hormone is reduced.
How serious is the interaction between Insulin degludec / insulin aspart and Levothyroxine?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor blood glucose more frequently when levothyroxine is started or its dose changed. Adjust the insulin dose as needed.
What other medicines interact with Levothyroxine?
MediHelp also lists interactions of Levothyroxine with, for example, Cholestyramine, Sodium iodide i-131, Tiratricol. The full list is on the Levothyroxine page.
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