It is rare when a woman should not breastfeed. The doctor may say not to breastfeed. The doctor may tell the mother not to take medicine that can be harmful to babies. If the mother has a sickness like HIV or active tuberculosis she may be told not to breastfeed. Check with the doctor before starting to breastfeed. Talk to the baby's doctor if the baby has a reaction to breast milk. This could be diarrhea, crying, or sleepiness.