What substance may interfere with the absorption of levothyroxine in a patient?

Calcium carbonate can interfere with the absorption of levothyroxine, which is a synthetic thyroid hormone used to treat hypothyroidism. The presence of calcium in the gastrointestinal tract can bind to levothyroxine, reducing its absorption and, consequently, its effectiveness. This interaction is significant because it can lead to inadequate levels of thyroid hormone in the body, resulting in persistent symptoms of hypothyroidism.

Patients taking levothyroxine are often advised to take it on an empty stomach and to avoid consuming calcium-rich foods or supplements around the time of taking their medication. This precaution is specifically due to the potential binding effect of calcium on levothyroxine, which disrupts its intended therapeutic action.

Understanding this interaction is crucial for managing patients on levothyroxine therapy to ensure optimal absorption and therapeutic outcomes.