Three months baby always crying may be related to hunger, vitamin D deficiency, gastrointestinal discomfort and other reasons. 1. Hunger: some babies have better digestion, or faster growth requires an increase in the amount of food, parents did not find in time, resulting in the baby is often in a state of hunger, there will also be often crying. 2. Vitamin D deficiency: vitamin D can promote calcium and phosphorus absorption and utilization. If the baby’s vitamin D intake is insufficient, it will cause low calcium. The child will show excessive sweating, crying, easy to startle, sleep disturbances and so on. 3. Gastrointestinal discomfort: It may be that the baby’s gastrointestinal system is not yet well developed, eating too much or lactose intolerance, as well as milk and protein allergies. All will cause indigestion, bloating, abdominal pain and other gastrointestinal symptoms, causing the baby to cry. Three-month-old babies always crying can also be seen in other reasons, it is recommended to consult a doctor in a timely manner, follow the doctor’s instructions for the relevant examination, with the help of the doctor to clarify the cause, and targeted treatment or treatment.