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

See the full Calcium page and Levothyroxine page for other reviewed interactions and reference information.

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.