First published on: Synthroid and calcium citrate are two important substances that often come into play in discussions about thyroid health. Many individuals taking Synthroid, a medication prescribed for hypothyroidism, may wonder about the impact of calcium citrate on their treatment. It’s crucial to understand that calcium citrate can interfere with the absorption of Synthroid if taken simultaneously. Therefore, it is generally recommended to space out these two substances to ensure optimal effectiveness. By doing so, patients can manage their thyroid condition more effectively while also addressing their calcium needs.