1. Low or high thyroid function (thyroid dysfunction)The thyroid gland is a butterfly shaped gland located in your neck. Thyroid hormone regulates your metabolism. Fatigue is a major symptom your thyroid is out of balance, it can happen in both hypo and hyperthyroidism. Getting a thorough thyroid panel will help you to determine if this is cause of your fatigue. Ask for the following labs: TSH, Free T3, Free T4, TPO, Thyroid autoantibody, Reverse T3. Also ask for a test of the nutrients that help your thyroid to function better such as: ferritin, vitamin D, B12. If these nutrients are low they are another reason for fatigue. 2. Low or high iron levels (iron dysfunction)Having too much or too little iron can cause fatigue. Low iron is often referred to as anemia. Often a CBC (complete blood count) is ran to screen for this but by the time this shows up in lab work the person is usually severely anemic. Thus ferritin is a better indicator for the need for iron supplementation because it measures the storage fo ...