Sudden weakness and sometimes chills may be caused by excessive fatigue, anemia, endocrine disorders and other reasons. 1. Excessive fatigue: generally excessive fatigue will trigger generalized pain, sudden weakness and sometimes chills. 2. Anemia: generally refers to the human body peripheral blood erythrocyte capacity is reduced, lower than the lower limit of the normal range, can not be adequate oxygen supply to the tissues and organs of a class of clinical syndromes, manifested as weakness, tinnitus, fatigue, dizziness, fainting, pale skin, fear of cold and other symptoms. 3. Endocrine disorders: such as hypothyroidism, manifested as reduced sweating, chills, slow movements, depression, irritability, fatigue and other symptoms. The above are only some of the common causes. If the symptoms persist or recur, you should consult a doctor. After a clear diagnosis, follow the doctor’s instructions to standardize the treatment.