levothyroxine sodium × omeprazole

Levothyroxine sodium requires gastric acidity to dissolve. Omeprazole raises gastric pH – thyroxine absorption falls by 20–30 %. Clinically this presents as rising TSH and failure to achieve targets in some patients.

Take levothyroxine strictly on an empty stomach, 30–60 minutes before food and other drugs. Take the PPI 2 hours later or in the evening. Check TSH at 6–8 weeks after starting omeprazole and, if needed, increase the levothyroxine dose by 12.5–25 µg.