Normal blood calcium is considered low if it is below 2.25 mmol/L. A lack of calcium in the body may lead to tingling and numbness in the face and lips, muscle spasms, and a feeling of dry skin. When the body is slightly deficient in calcium, neuromuscular excitability increases, which is usually manifested as abnormal sensations, such as tingling and numbness in the hands and feet, face, and lips. When the symptoms of calcium deficiency continue to worsen, the human body will have serious skeletal muscle and smooth muscle spasm will appear hand and foot twitching, muscle spasm, as well as dry, inelastic skin, gray color. When calcium deficiency is severe, the large loss of calcium may lead to bone pain, pathologic fracture, bone deformity, bone softening and so on. As well as causing abnormalities in the cardiovascular system, such as conduction block and other cardiac arrhythmias, and in severe cases, ventricular fibrillation, etc., with panic and a sense of breathlessness. When the body is deficient in calcium, timely calcium supplementation is usually required. This can be done through dietary calcium supplements and medications as prescribed by the doctor, such as calcium carbonate and calcium lactate. Dietary milk and dairy products are the most common, which are not only high in calcium but also easily absorbed.