There are more causes of calcium deficiency in adolescents, including genetic factors, untimely calcium supplementation, improper calcium supplementation, and poor lifestyle habits, such as excessive intake of coffee and cola, which lead to excessive calcium loss. When adolescents have symptoms of low calcium, they often show skeletal abnormalities, mental abnormalities, digestive system abnormalities, cardiovascular abnormalities, endocrine abnormalities, etc. If the symptoms of calcium deficiency appear, it is recommended to go to the hospital in time to improve the examination, clarify the cause and actively cooperate with the treatment.1. Skeletal abnormalities: When adolescents are deficient in calcium, the bones will be stunted, which will cause bone degeneration earlier and easy to fracture. It may also lead to the occurrence of adolescent rickets due to the lack of vitamin D. It will manifest as slow growth and skeletal deformities, such as O-leg and X-leg. Due to the lack of calcium in bone, the bone like tissue lacks weight bearing capacity, the long bone stem becomes bent under the effect of gravity, the tibia and femur are easily deformed, forming bow legs or also called O-leg, which may also be accompanied by brittle nails, rough hair and dry skin; 2. Mental abnormalities: there may also be neurological symptoms such as anxiety, depression, drowsiness, etc. Due to the decrease of serum calcium ion concentration and the increase of neuromuscular excitability, hypocalcemia will also appear, which is manifested as depression, poor spirit, easy agitation, twitching of hands and feet, muscle spasm, numbness around the mouth and the end of the limbs, and even pins and needles; 3. Digestive system abnormalities: calcium deficiency in adolescents may lead to digestive system abnormalities, with manifestations such as loss of appetite, indigestion, paranoia, anorexia, constipation, etc.; 4. Cardiovascular abnormalities: too little calcium intake, the proportion of blood pressure increases, calcium absorption decreases will lead to calcium ion channel block segment, extracellular calcium ions can not enter the cell, easily cause blood pressure to rise. Calcium can play the role of relaxation of blood vessels and smooth muscle, calcium deficiency will make the intracellular calcium into the blood circulation, smooth muscle can not relax, causing hypertension; 5, endocrine abnormalities: calcium deficiency in adolescents may cause endocrine disorders, endocrine function metabolic abnormalities; 6, other abnormalities: calcium deficiency may easily cause bleeding, may also cause loose teeth, tooth misalignment or even early loss. Calcium deficiency in adolescents is prone to weakness, lack of concentration, dizziness, memory loss, and even lower immunity and infections and osteochondrosis. Calcium deficiency in adolescents should be supplemented in a timely manner. Calcium supplementation is a long-term process that cannot be effective in the short term, and the calcium in the bones is constantly being updated, so it is important to insist on long-term calcium intake to ensure bone health. Pay attention to your diet, consume more milk and beans, take calcium supplements as appropriate, and exercise more to increase bone density and body balance. You can also get more sunlight and take vitamin D supplements to facilitate the absorption of calcium. But it is not recommended to take too much calcium, too much can easily cause urinary stones.