Mild calcium deficiency is characterized by irritability, crying, not easy to put to sleep, often waking up after falling asleep, crying, sweating, especially when breastfeeding, yellow and thin hair, hair loss at the back of the head, commonly known as “occipital baldness”; moderate calcium deficiency is characterized by low resistance, easy to catch a cold, fontanelle closure, teething, walking later than children of the same age; severe calcium deficiency will result in rickets. Severe calcium deficiency can lead to rickets symptoms such as chicken chest, hunchback, rotundity and muscle weakness. The main symptoms of calcium deficiency in children are as follows: 1. night sweating, especially after sleep, sweating, sweating after crying is more obvious. 2. 2, sleep is not real, night terrors, night cries. Often wake up suddenly at night and cry more than once. 3, abnormal temperament, strange temperament, crying, fidgeting, not easy to take care of. 4.Pillow baldness circle, because the child is irritable and does not fall asleep easily, his head keeps rubbing the pillow, and the hair at the back of the head is worn out over time, forming pillow baldness. 5. Late teething, uneven teething, some children still have not teething at the age of 1.5 years, or have poorly developed teeth, uneven teeth arrangement, improper bite, loose teeth, and premature loss. 6.Nails are gray or have white marks. 7.Skeletal abnormalities include square cranium, rib cage exostosis, rib cage bead, bracelet ankle bracelet sign, chicken chest, funnel chest, and serious O-leg or X-leg. 8.Severe low calcium may also cause hypocalcemic convulsions.