Calcium carbonate × Levothyroxine sodium

Calcium binds levothyroxine in the gut as insoluble complexes, reducing absorption by 20–25%.

Return of hypothyroidism: fatigue, weight gain, cold intolerance, dry skin, low mood. In thyroid cancer, loss of TSH control.

Take levothyroxine in the morning on empty stomach, 30–60 minutes before food and other drugs. Take calcium carbonate 4 hours after levothyroxine (e.g. at lunch or in the evening). Check TSH 6–8 weeks after starting calcium.