Introduction: Hypothyroidism is a relatively common disease, and patients are often treated with levothyroxin however when high doses of levothyroxin are needed for its treatment of hypothyroidism, we should carefully consider the reasons. Case report: A 43 year old woman, suffering from uncontrolled hypothyroidism, referred to an endocrine clinic, was treated with 1000 microgram levothyroxin and 150 microgram liothyronin tablets. She admitted to hospital with a likely diagnosis of levothyroxin false malabsorbtion to take the levothyroxin loading test. Results: Serum T4 was measured at 0, 30, 60,120 and 240 minutes after levothyroxin consumption and showed increases in serum T4 level was 0.9, 1.2, 1.4, 2.3, 2.6 μg/dL respectively. Absorption of T4 was normal in the small bowel, due to false levothyroxin malabsorbtion that had occurred because of irregular drug consumption. Conclusion: Levothyroxin loading test can differentiate between true and false malabsorbtion. Considering the high prevalence of psychological symptoms, depression in particular, in hypothyroid patients who do not responsd to treatment despite increased the doses of levothyroxin, levothyroxin malabsorbtion needs to be researched, especially the false type and following a definite diagnosis, appropriate treatment can be prescribed.