Many things can reduce your breast milk supply, ranging from how often you nurse to medications you might take without thinking twice. Some causes are temporary and easy to fix, while others require more attention. Understanding what’s working against your supply is the first step to protecting it.
Infrequent Feeding or Pumping
The single biggest factor in milk production is how often milk is removed from the breast. Your body operates on a supply-and-demand system: the more frequently and thoroughly your breasts are emptied, the more milk they produce. When milk sits in the breast for extended periods, a signaling process kicks in at the cellular level. Proteins in the milk itself accumulate and tell the milk-producing cells to slow down. This is why skipping feedings, stretching intervals too long, or supplementing with formula without pumping can cause a noticeable drop in supply within days.
This feedback loop works in both directions. If you suddenly start nursing or pumping more often, supply typically increases within 48 to 72 hours. But if you let the breast stay full repeatedly, the signal to reduce production gets stronger each time. A poor latch can have the same effect, since the baby isn’t effectively draining the breast even though they’re at it frequently.
Medications That Lower Supply
Some common over-the-counter and prescription medications can quietly reduce how much milk you make. The most well-documented culprit is pseudoephedrine, the decongestant found in many cold and sinus products. A study of breastfeeding mothers found that a single 60 mg dose reduced milk production by 24% over 24 hours, likely by suppressing prolactin, the hormone that drives milk synthesis. That’s a significant drop from one dose of something you might grab off the pharmacy shelf without a second thought.
Antihistamines, particularly the older sedating types like diphenhydramine, are also associated with reduced supply in some women, though the evidence is less precise. If you’re congested or dealing with allergies while breastfeeding, saline sprays or nasal steroid sprays are generally safer choices for your supply.
Hormonal Birth Control
Not all contraception affects milk supply equally. Estrogen-containing methods, including combined oral contraceptive pills, the patch, and the ring, are the most likely to cause problems. One trial comparing combined pills to progestin-only pills found that combined pill users experienced a 42% reduction in milk volume from weeks 6 to 24 postpartum, compared to a 12% reduction in the progestin-only group. The average volume difference between the two groups widened over time, reaching about 25 mL less per day by 24 weeks.
Progestin-only options (the minipill, hormonal IUDs, the implant, and the injection) are considered more compatible with breastfeeding. If you’re concerned about supply and want hormonal contraception, starting with a progestin-only method is the standard recommendation. Timing matters too. Introducing any hormonal method in the first few weeks postpartum, before your supply is well established, carries more risk than waiting until six to eight weeks.
Stress and Sleep Deprivation
Stress doesn’t reduce how much milk your body makes so much as it blocks your body’s ability to release it. The let-down reflex, the process that pushes milk from deep in the breast toward the nipple, is triggered by oxytocin. Stress hormones can directly inhibit oxytocin release, making let-downs slower, weaker, or harder to trigger. You might have plenty of milk in the breast but struggle to get it out, which then feeds the cycle: less milk removed means less milk produced.
This is why some mothers notice their pump output drops dramatically during a stressful week even though nothing else has changed. Sleep deprivation compounds the problem by raising baseline stress hormones and disrupting the normal hormonal rhythms that support lactation. The fix isn’t always as simple as “relax,” but understanding that stress targets the release mechanism rather than the production machinery can help. Warmth on the breast, skin-to-skin contact, and minimizing distractions during feeds or pumping sessions can all help coax a stubborn let-down.
Underlying Health Conditions
Some mothers face supply challenges rooted in hormonal or medical issues that existed before pregnancy. Polycystic ovary syndrome (PCOS) is one of the more common ones. In a survey of mothers with PCOS, a third reported insufficient milk supply. The hormonal profile of PCOS can interfere with breast development during pregnancy and with milk production afterward in several ways: high androgen levels may blunt the receptors that respond to prolactin, progesterone imbalances can disrupt the growth of milk-producing tissue, and insulin resistance may hinder the breast’s ability to use insulin in the milk-making process.
Thyroid disorders, particularly hypothyroidism (an underactive thyroid), can also lower supply because thyroid hormones play a supporting role in prolactin function. The good news is that once thyroid levels are properly managed with medication, supply often improves. Other conditions linked to primary low supply include insufficient glandular tissue (where the breast simply didn’t develop enough milk-producing cells), prior breast surgery that severed milk ducts or nerves, and significant postpartum hemorrhage, which can damage the pituitary gland and reduce prolactin production.
Certain Herbs and Foods
You’ll find long lists online of herbs said to decrease milk supply, but the evidence behind most of them is thin. Sage is the most consistently cited herb with lactation-suppressing properties, used as a tea, dried herb, or tincture. It has a long history of traditional use for reducing supply during weaning, and many lactation consultants consider it effective based on clinical experience.
Peppermint, spearmint, parsley, and oregano also appear on these lists, but there’s an important distinction: normal dietary amounts of these herbs, including drinking the occasional cup of peppermint tea, are unlikely to affect your supply. The concern applies to concentrated or medicinal doses consumed repeatedly. If you’re eating pesto or adding fresh mint to a salad, you don’t need to worry. If you’re drinking six cups of peppermint tea a day, that’s a different story.
Rapid Weight Loss and Caloric Restriction
Breastfeeding burns roughly 300 to 500 extra calories per day. Severe caloric restriction, crash dieting, or very rapid weight loss can signal to your body that resources are scarce, which may reduce milk production. Gradual, moderate weight loss of about one to one and a half pounds per week is generally well tolerated during breastfeeding. But dropping below roughly 1,500 to 1,800 calories per day (depending on your size and activity level) puts you in territory where supply can take a hit.
Dehydration on its own is often blamed for low supply, but the evidence is less clear-cut than most people assume. Mild dehydration doesn’t dramatically reduce milk volume in otherwise healthy mothers. That said, severe dehydration or illness with significant fluid loss can absolutely affect production. Drinking to thirst is a reasonable guideline; forcing excessive water intake beyond what you’re thirsty for doesn’t boost supply.
Smoking and Alcohol
Nicotine reduces prolactin levels and can inhibit the let-down reflex, creating a double hit to supply. Mothers who smoke tend to produce less milk and breastfeed for shorter durations on average. The effect is dose-dependent, meaning heavier smoking has a greater impact.
Alcohol in moderate amounts (one drink) doesn’t permanently reduce supply, but it temporarily suppresses oxytocin and can delay the let-down reflex for a few hours after consumption. Regular heavy drinking, however, can meaningfully lower overall production. The timing also matters: milk output is typically lowest in the two to three hours after a drink.
Pregnancy
If you become pregnant while breastfeeding, the hormonal shifts of early pregnancy, particularly rising progesterone, will almost always reduce your milk supply. This typically starts around the end of the first trimester, though some mothers notice changes even earlier. By mid-pregnancy, supply often drops substantially regardless of how frequently you nurse. This is hormonally driven and not something you can overcome with increased demand. Some mothers continue nursing through pregnancy and then tandem nurse after the new baby arrives, but the supply dip during pregnancy itself is essentially unavoidable.