In the current randomized double blind placebo controlled trial, 40 patients with hashimoto thyroiditis are enrolled. Patients are divided into two intervention and placebo groups with random permuted block and are matched according to age, gender and drug dosage. After signing written informed consent anthropometric parameters including weight, height and BMI will be measured and subjects in intervention and control group will receive 1 gram/day packages of Nigella Sativa or placebo for four weeks. The study's inclusion criteria are as follows: aged between 20-50 years old, diagnosis of Hashimoto thyroiditis by physician, completing written informed consent. Exclusion criteria are: pregnancy, lactation, taking supplements such as vitamin E, C, zinc, folate, cobalamin and phytoestrogens in past three months, any history of celiac, cardiovascular disease, arthritis, autoimmune and inflammatory disease, thyroid abnormalities and surgeries, and being on any special diets.