Getting up in the morning with weak and achy legs may be caused by physiological reasons, low blood potassium, hypothyroidism and other factors. 1. Physiological reasons: such as after strenuous exercise, it may cause lactic acid accumulation, lactic acid will stimulate the nerve endings, causing the symptom of getting up in the morning with weak and achy legs. 2. Low blood potassium: Potassium ions are important substances involved in cellular bioelectrical activity. When blood potassium is lowered in the body, the electrical activity of nerve cells and muscle cells is affected, thus leading to aching and weakness of legs. 3. Hypothyroidism: hypothyroidism patients with reduced synthesis of thyroid hormones in the body will cause the body’s metabolism to decrease, resulting in getting up with the symptom of weak and achy legs. If you exclude physiological factors, you should go to the hospital in time to improve the examination and standardize the treatment after the cause is clear.