After developing diabetes mellitus, symptoms like reduced vision, joint pain, and weakness in the hands and legs can occur if blood sugar is not well controlled. High sugar levels can affect the eyes and nerves, which may cause weakness or pain. It is important to keep your blood sugar under good control, take diabetes medicines regularly, follow a healthy diet, regular exercise, and routine eye and nerve check-ups. If vision changes or weakness continues, consult your doctor so they can check your blood sugar levels, vitamins, and nerve health and adjust treatment if needed.