I am very tired all of a sudden with having energy one minute & the next i cant really do anything what could the cause be thank u?

Doctor can evaluate: Extreme tiredness is not normal and needs an evaluation. One's primary care doctor can look for causes such as anemia, cancer, infections, hormonal imbalances, depression, etc... Thyroid hormone problems are one of the many possible causes. One can write down a list of symptoms, and when each started, to take to the doctor. In her mid-30's, fatigue should be fixable if the cause is found.