Hi, One of the causes of a raised homocysteine level is Vitamin B12 deficiency . Raised homocysteine levels are also a risk factor for diseases such as heart attack ( medically called myocardial infarction) , stroke etc. In fact a rise in homocysteine levels detects even early phases of Vitamin B12 deficiency. As you have been diagnosed with Hashimoto s disease which is an immune mediated disease you may be prone to develop immune mediated diseases in other organs as well. An immune mediated disease is one where certain molecules called autoantibodies attacks its own cells and tissues . There is a possibility that you may have a condition called PERNICIOUS ANEMIA which is known to occur in some patients with Hashimotos. Pernicious anemia is a common cause of B12 deficiency. A protein called intrinsic factor, made by parietal cells that line the stomach, is needed for B12 absorption. In pernicious anemia, inflammation damages the parietal cells, leading to little or no intrinsic factor, thus preventing the intestines from absorbing B12. I would advise you to do the following tests Intrinsic factor antibody test Parietal cell antibody test If any of these tests are positive then there is the possibility that you also have PERNICIOUS ANEMIA. In addition to this please also do a Fasting blood sugar and Post prandial blood sugar test to detect Diabetes mellitus which may be associated with your condition. All of the above contribute to loss of weight and a feeling of exhaustion. You should also recheck your THYROID FUNCTION TESTS ( TSH, T3 and T4 ). I presume that you may be taking medication for Hashimotos. You should take life long Vitamin B12 if you have Pernicious anemia. To correct the Vitamin B12 deficiency due to Pernicious anemia one of the methods is to take 1000 mcg IM/SC injections once daily for 7 days, then weekly for 1 month, then monthly. There is also a nasal spray option:Nasal spray: 500 mcg (1 spray in 1 nostril) weekly.