yes this is a classic example of how a vitamin or supplement can effect a prescription medication. the calcium citrate inhibits the absorption of the levothroid which means your body will not get the dose of the thyroid medication it needs. this can lead to hypothyroidism. i suggest taking your levothroid in the morning and the calcium citrate in the afternoon to avoid this interaction. if you have any questions about medications talk to your pharmacist we are happy to help.
does taking calcium citrate interfere with taking my thyroid medicine levothroid?