The fact that you have milk but can’t suck it out can be caused by milk blockage, nipple inversion, mastitis and so on. 1. Breast milk blockage: If the channel for milk secretion is stagnant, the milk will be stagnant inside the breast, thus forming a hard knot. The blockage will prevent the milk from flowing out smoothly, causing the breasts to swell and forming a milk blockage, resulting in a situation where the milk is available but cannot be sucked out. 2. Nipple inversion: Nipple inversion is mainly manifested as the patient’s nipple does not protrude from the areola plane, or even sunken below the skin surface, resulting in a localized crater, and there is a ring-shaped bulge around the sunken area. When the patient’s nipple has the symptom of inversion, it is difficult for the baby to hold the nipple and suck, and the phenomenon of having milk but not sucking it out will occur. 3. Mastitis: Mastitis is usually an inflammation of the breast tissue and can be divided into breastfeeding and non-breastfeeding mastitis. Mastitis is mainly characterized by breast pain, redness, swelling, and fever, and further development of breast abscesses can be formed, which may also lead to breast milk, but can not be sucked out. When the patient has milk but can’t suck it out, it is recommended to go to the hospital as soon as possible for relevant examination and treatment, so as to avoid delaying the condition or affecting breastfeeding.