There may be milk when sucking without pregnancy, but it is usually an abnormal phenomenon, which may be caused by overdose of birth control pills, pituitary tumor, mammary gland hyperplasia and other reasons for overflow. Women who are not pregnant do not normally secrete milk, which needs to be stimulated by prolactin to be secreted. After a woman is pregnant and has given birth, the prolactin level in her body rises, which stimulates the milk ducts and breast lobules to secrete milk. If you are not pregnant and sucking on the breast, you should consider that it is abnormal, for example, oral overdose of birth control pills causes the pituitary gland to secrete prolactin, prolactin increases and there will be overflowing of breasts, and sucking on the breast will have milk secretion. Patients with pituitary tumor will cause abnormal hormone secretion in the body, prolactin is one of the hormones secreted by the pituitary gland, causing prolactin to increase will have the manifestation of overflowing breasts, and there will be breast milk when sucking without being pregnant. Patients with breast hyperplasia, breast duct dilation after breast hyperplasia lesions, may cause nipple overflow, sucking will also have milk discharge. It is recommended to go to the hospital to check the cause of breast milk discharge when sucking without pregnancy.