Can You Take Calcium and Levothyroxine Together?

Calcium can reduce how much levothyroxine your body absorbs -- the FDA label recommends spacing them at least 4 hours apart.

Use cautionEvidence: High

What the interaction means

Levothyroxine's FDA prescribing information lists calcium carbonate among the agents that may decrease absorption of the medication: "Calcium carbonate may form an insoluble chelate with levothyroxine, and ferrous sulfate likely forms a ferric-thyroxine complex. Administer levothyroxine sodium capsules at least 4 hours apart from these agents."

Why it may happen

Calcium carbonate can bind with levothyroxine in the gastrointestinal tract, forming a complex that isn't absorbed the same way, which can lower how much of the medication actually reaches the bloodstream.

Practical context

This is a well-established interaction reflected directly in levothyroxine's FDA labeling, not an emerging or uncertain one. Levothyroxine is already recommended to be taken on an empty stomach, one-half to one hour before breakfast; the same 4-hour spacing recommendation that applies to calcium is also given for other absorption-interfering agents such as iron supplements.

Timing

A spacing interval of about 240 minutes is documented in the sources below.

What the sources say

Levothyroxine Sodium Capsules — FDA Prescribing Information — YARAL Pharma, Inc. (via DailyMed, U.S. National Library of Medicine)

Last reviewed 2026-08-22

Medical information disclaimer: this information is general and educational. It does not diagnose conditions, prescribe treatment, or determine whether a combination is safe for you personally. Follow your prescription label and ask a pharmacist or clinician before starting, stopping, or combining products. Full disclaimer.