Over-the-Counter Drugs, Herbal Supplements, Vitamins, And Minerals Practice Test

When taking levothyroxine, absorption in the gut can be affected by minerals that bind the drug in the intestinal lumen. Calcium is one of the common culprits; calcium supplements can chelate levothyroxine, forming insoluble complexes that reduce how much of the hormone is absorbed into the bloodstream. That’s why taking calcium at the same time as levothyroxine can lower the amount of medication that gets into circulation, potentially leading to persistent hypothyroid symptoms or an elevated TSH. To avoid this interaction, space the doses—levothyroxine is generally taken on an empty stomach first thing in the morning, with about a 4-hour gap before taking calcium, iron, magnesium, or other mineral supplements. While other minerals can also interfere, calcium is the classic example highlighted here. If you need both, coordinate timing with a clinician to adjust dosing as needed.