Low milk supply has many possible causes, and most of them are fixable. The most common reason is simply that milk isn’t being removed from the breast often or thoroughly enough, which signals your body to slow production. Hormonal shifts, certain medications, and less common anatomical factors can also play a role. Understanding what’s behind your supply issue is the first step toward increasing it.
How Your Body Decides How Much Milk to Make
Milk production works on a supply-and-demand system, but it’s more precise than most people realize. Your breasts contain a protein called the feedback inhibitor of lactation, or FIL, that accumulates in milk as it sits in the breast. When milk stays in the breast too long, FIL builds up and tells the milk-producing cells to slow down. When milk is removed (by nursing or pumping), FIL is removed too, and production picks back up.
This is why each breast regulates itself independently. If your baby consistently favors one side, the other side can gradually decrease output on its own. It’s also why the single most effective thing you can do for supply is remove milk more frequently and more completely. Your body reads that demand signal and responds.
In the earliest days, a different system is in charge. When the placenta detaches at delivery, progesterone levels drop sharply. That drop, combined with high levels of prolactin and other hormones, triggers the transition from colostrum to mature milk. This shift typically happens between days two and five postpartum. Once that transition is complete, the ongoing amount of milk you produce depends less on hormones and more on how often and how well milk is being removed.
Are You Actually Low on Milk?
Many parents worry about supply when their baby is actually getting plenty. Breast softness, shorter feeds, or a fussy baby aren’t reliable indicators of low milk. The most dependable signs come from the other end: your baby’s diapers and weight gain.
In the first few days, diaper counts should roughly match your baby’s age in days. One wet diaper on day one, two on day two, three on day three. From day four onward, expect four to six wet diapers every 24 hours. For weight, healthy newborns typically gain about an ounce a day, or four to seven ounces per week in the first few months. Most babies lose some weight in the first few days after birth, but should return to their birth weight by about two weeks. If your baby is meeting these benchmarks, your supply is likely fine even if it doesn’t feel that way.
The Most Common Cause: Not Enough Milk Removal
If supply genuinely is low, the first thing to evaluate is frequency. Newborns need to nurse at least 8 to 12 times in 24 hours. Stretching feeds to a schedule, skipping nighttime sessions, or using a pacifier heavily in the early weeks can all reduce the demand signal your body receives. A shallow latch also matters: if your baby isn’t transferring milk efficiently during a feed, your breasts don’t get the “empty” signal they need, and FIL accumulates.
Signs of a poor latch include nipple pain that doesn’t improve after the first few seconds, a clicking sound during feeding, or a baby who seems to be working hard but not swallowing regularly. A lactation consultant can assess latch and transfer in a single visit, and this alone resolves supply problems for many parents.
Hormonal and Medical Causes
Sometimes the issue isn’t behavioral but hormonal. Thyroid problems are one of the more common medical culprits. Thyroid hormones directly influence how much milk your body produces and even affect milk’s protein content. An underactive thyroid is roughly eight times more common in women than men, and postpartum is a particularly vulnerable time for thyroid shifts. If you’re experiencing fatigue beyond normal new-parent exhaustion, unexplained weight changes, hair loss, or feeling unusually cold, a simple blood test can check your thyroid levels.
Retained placental fragments are a less common but significant cause. Your milk supply depends on that post-delivery drop in progesterone. If small pieces of placental tissue remain in the uterus, they continue releasing progesterone and can block your body from ramping up production. The telltale sign is that mature milk simply never “comes in” despite frequent nursing. Once the retained tissue is removed, milk production typically begins promptly. Heavy or prolonged postpartum bleeding can be another clue.
Other hormonal factors include polycystic ovary syndrome (PCOS), diabetes, and a history of fertility treatments, all of which can affect the hormonal cascade that drives milk production. Significant blood loss during delivery or a traumatic birth can also delay the process.
Medications That Can Lower Supply
Certain over-the-counter medications can quietly sabotage milk production. Pseudoephedrine, the decongestant found in many cold and allergy medicines, is one of the worst offenders. A single 60-milligram dose reduced daily milk output by 24% in one study, dropping average production from about 784 milliliters to 623 milliliters per day. That’s a significant hit from one dose of something you might take without thinking twice.
Hormonal birth control containing estrogen can also lower supply, particularly if started in the first few months postpartum. Some antihistamines and certain blood pressure medications have similar effects. If you’ve noticed a supply drop that coincided with starting any new medication, it’s worth checking whether it could be the cause.
Breast Anatomy and Glandular Tissue
A small percentage of women have insufficient glandular tissue, meaning their breasts didn’t develop enough milk-producing tissue during puberty or pregnancy. Physical markers that may suggest this include a wide space between the breasts (more than about 1.5 inches), very little breast growth during pregnancy (less than one cup size increase), significant asymmetry (two or more cup sizes different), stretch marks that appeared before a first pregnancy, or breasts that are tubular in shape rather than round.
Having one of these features doesn’t mean you can’t breastfeed. Many women with atypical breast shapes produce plenty of milk. But when several of these markers are present alongside genuinely low output despite frequent nursing, insufficient glandular tissue may be part of the picture. In these cases, partial breastfeeding with supplementation is often a workable approach. Breast size alone, for what it’s worth, has no relationship to milk-producing capacity. Larger breasts simply contain more fatty tissue, not necessarily more glandular tissue.
How to Increase Your Supply
The foundation of any supply-boosting strategy is removing more milk, more often. Nursing or pumping every two to three hours during the day, including at least once overnight, gives your body the strongest possible demand signal. If you’re pumping, make sure your flange size is correct, as a poorly fitting flange compresses the milk ducts and reduces output.
Power pumping is a technique that mimics cluster feeding to signal your body to produce more. In a single hour, you pump for 20 minutes, rest for 10, pump for 10, rest for 10, then pump for a final 10 minutes. Doing this once a day for two to three days is typically enough to see results, after which you return to your normal routine.
Skin-to-skin contact with your baby also supports production by encouraging prolactin release. Stress and sleep deprivation work against supply, though they rarely cause low supply on their own. They’re more likely to compound an existing issue.
Do Galactagogues Work?
Fenugreek is the most widely recommended herbal supplement for milk supply, typically taken in doses of 1 to 6 grams daily. The evidence, however, is underwhelming. One meta-analysis found a mild effect, while another found no good evidence that it works at all. A controlled study looking at fenugreek seed capsules found no increase in milk volume at day four, and only very low certainty evidence of any effect by day ten. Some women report noticing a difference, but it’s difficult to separate the herb’s effect from the increased nursing or pumping that usually accompanies it. Fenugreek can also lower blood sugar, which matters if you have diabetes or are taking related medications.
Other commonly suggested galactagogues like oats, brewer’s yeast, and blessed thistle have even less research behind them. They’re unlikely to cause harm, but placing your energy on more frequent milk removal will almost always yield better results than any supplement.
When Supply Problems Start Later
Some parents have a solid supply in the early weeks that drops off around three or four months. This is often misread as a supply problem when it’s actually a normal shift. Early on, your body overproduces as a safety margin. Over time, production calibrates to what your baby actually needs. Your breasts may feel softer and less full, letdown may feel less dramatic, and pumping output might dip slightly. None of this means you’re producing less than your baby requires.
True later-onset supply drops can happen when returning to work introduces longer gaps between feeds, when a baby starts sleeping through the night (removing those overnight demand signals), or when a medication change occurs. Reintroducing more frequent milk removal usually brings supply back within a few days, since the FIL-based system responds relatively quickly to changes in demand.