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How Breasts Make Milk


Your breasts contain small sacs called mammary glands. These glands make breast milk. The milk travels from the mammary glands through tubes in your breasts called ducts. The milk collects in an area called the sinus. When your baby breastfeeds, the milk moves from the sinus out of the breast through tiny holes in the nipple.

Picture of a normal breast


Take your medicine as directed:

Call your primary healthcare provider if you think your medicine is not helping or if you have side effects. Tell him if you are allergic to any medicine. Keep a list of the medicines, vitamins, and herbs you take. Include the amounts, and when and why you take them. Bring the list or the pill bottles to follow-up visits. Carry your medicine list with you in case of an emergency.

Ask for information about where and when to go for follow-up visits:

For continuing care, treatments, or home services, ask for more information.

The stages of making milk:

Your breasts go through four stages when making milk:

  • Stage 1: This stage begins in your second trimester (months 4 to 6) of pregnancy. Hormones (chemicals in your body) are released that tell your mammary glands to start making milk. In the first 24 to 48 hours after you give birth, your breasts produce a small amount of colostrum. This thick substance is the first milk your body makes for your baby.
  • Stage 2: This stage begins about 3 to 5 days after you give birth, when your mature milk comes in. Your breasts will feel fuller as they increase the amount of milk they produce. It may take 6 to 10 days for your milk to come in. Health problems such as diabetes or obesity (weighing more than your caregiver suggests) may cause a delay. A cesarean section or flat or inverted (pointing in) nipples may also cause a delay.
  • Stage 3: This stage starts when your baby is about nine days old. It continues until you stop breastfeeding. During stage 3, you must regularly remove milk from your breasts for them to keep making milk. Remove milk by nursing your baby or by expressing. Expressing is when you remove breast milk with your hands or with a pump.
  • Stage 4: This stage lasts about 40 days after your last breastfeeding session. During this stage, your milk production will slowly decrease and stop.

Contents of breast milk:

  • Breast milk is the best food for your baby. It contains many nutrients that help your baby grow. Breast milk also contains antibodies (cells that fight infection). Antibodies help protect your baby against health problems such as diarrhea, lung infections, and ear infections.
  • The contents of your breast milk change to meet the needs of your baby as he grows. Colostrum contains high levels of protein, some minerals, and low amounts of sugar. Colostrum also contains antibodies. Mature milk contains a lower amount of protein, and higher amounts of sugar, vitamins, minerals, and fat. Your baby gets the highest amount of nutrients at the end of the breastfeeding session. Breastfeed your baby until your milk flow stops to help your baby get the most nutrients.

Milk let-down:

Let-down is when your breast milk flows to your nipples. You may have a tingling, tight feeling in your breasts during let-down. You may have more than one let-down during each breastfeeding session. Let-down may happen when your baby latches on to breastfeed. It may also happen when you see, hear, or think of your baby.

Caring for yourself when breastfeeding:

  • Eat a healthy diet. Eat healthy food to help your body make enough breast milk. You should also drink at least eight 8 ounce cups of liquid each day. Your caregiver may have you take vitamins, such as vitamin D. Talk with your caregiver before you take any vitamins or supplements. Do not diet to lose weight when you are breastfeeding. Talk with your caregiver about the foods you should eat and how much. Together you can plan the best diet for you.
  • Manage your stress. Increased stress can decrease your supply of breast milk. Relaxation can help reduce your stress and help you feel better. Deep breathing, meditating, and listening to music also may help you cope with stress. Talk to your caregiver about other ways to manage stress.
  • Talk to your caregiver before you take any medicines. This includes all prescription and nonprescription (over-the-counter) medicines. Some medicines may decrease the amount of breast milk you make. Other medicines may enter your breast milk and harm your baby.
  • Do not smoke. If you smoke, it is never too late to quit. Smoking can decrease the amount of breast milk you make. Smoking harms your body in many ways. You are more likely to have heart disease, lung disease, cancer, and other health problems if you smoke. Quitting smoking will improve your health and the health of those around you. Talk with your caregiver if you smoke and need help to quit.
  • Limit or avoid alcohol. Breastfeed your baby before you drink alcohol. Do not breastfeed your baby for at least 2 to 2 ½ hours after having one drink. One drink of alcohol is 12 ounces of beer or 4 ounces of wine. One ounce of liquor, such as whiskey, is one drink of alcohol. Talk to your caregiver if you drink alcohol and are breastfeeding.
  • Go to all follow-up visits with your caregiver. Ask your caregiver when to return for follow-up visits. Keep all appointments. Write down any questions you have. This way you will remember to ask these questions during your next visit.

For support and more information:

Breastfeeding can be hard. It may help to learn as much as you can about breastfeeding. Your caregiver may have you see a specialist called a lactation consultant to help you with breastfeeding. You can also contact the following:

  • American Academy of Pediatrics
    141 Northwest Point Boulevard
    Elk Grove Village , IL 60007-1098
    Phone: 1- 847 - 434-4000
    Web Address:


  • Your milk has not come in within five days of giving birth. Your milk has come in if your breasts feel full or swollen. Your breasts may also be leaking milk.
  • You feel you are not making enough breast milk for your baby.
  • Your breasts do not feel full before feedings and softer after breastfeeding.
  • Your baby is breastfeeding fewer than eight times each day.
  • Your baby is four or more days old and has fewer than six wet diapers each day.
  • Your baby is four or more days old and has fewer than three stools each day.


  • Your baby shows signs of dehydration, such as sunken eyes, dry skin, fast breathing, or few or no wet diapers. He may also act very tired, irritable, or unwell, or he may not be responding to you. He may also have a very fast heartbeat.
  • You are feeling so sad that you want to hurt your baby or yourself.

The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.