Determine thyroid hormone prescription patterns in the population covered by the Colombian Social Security Health System.Descriptive study using a database of 6.2 million people. The selected patients, men and women of all ages, received continuous thyroid hormone treatment from April to June 2013. A database on medication use was designed, using data obtained by the company that dispenses these drugs.It was found that 29 947 patients in 82 Colombian cities had been treated for hypothyroidism. The majority (79.1%) were women, with an average age of 63.2 ± 16.1 years. The most common prescription was for levothyroxine in 50 µg tablets (85.7%) at higher-than-recommended daily dosages, especially as monotherapy. Significant differences between age groups and cities of residence were found for the combined use of thyroid hormone and co-medication. The most frequently prescribed concomitant drugs were antiulcer agents (44%), hypoglycemics (17.4%), and iron salts (16.1%).There are significant differences in prescribing practices in the cities studied. Clinical management guidelines that standardize dosages and physicians' practices are needed, since a lack of guidelines has likely had an impact on patients' health. The clinical efficacy of the prescriptions studied should be explored.