By Hilary Metcalfe

The first time my supply dropped I was three months in and had just started to feel human again. Late afternoon, slow let-down, and barely anything in the bottle. I did what most of us do at that hour on that little sleep. I panicked, I googled, and I started counting ounces as though they were evidence of whether I was enough.

Nobody had told me that supply moves in rhythms. Daily ones. Monthly ones. Ones that arrive with a growth spurt, a returned period, a new prescription, a fortnight of not eating properly. Almost none of them mean your body has failed, and nearly all of them are predictable once you know they exist.

What follows is every dip I have since learned to name. When it happens, why, which ones resolve on their own, and which ones are structural and deserve a doctor rather than another article telling you to feed more often.

First, how supply actually works

Milk runs on two systems, and the difference between them explains almost everything that follows.

The first is hormonal, and it dominates the early weeks. When the placenta leaves, progesterone drops and prolactin surges, and your milk comes in whether or not you do anything about it. Which is why those first days feel automatic and often overwhelming.

The second takes over from around two weeks and runs on supply and demand. Milk removed is milk made. There is a protein in breastmilk called feedback inhibitor of lactation that works something like a thermostat. When a breast stays full, it builds up and tells that breast to slow down. When the breast is drained often, it clears and production climbs. Your body is measuring how much milk left the building, and nothing else.

Nearly every dip below is one of those two systems doing exactly what it was designed to do.

The daily dip

Supply is not flat across twenty-four hours and was never meant to be.

Prolactin follows a circadian rhythm. It peaks overnight and sits at its lowest in the late afternoon and early evening, which is why the 5pm pump that terrifies so many women yields so little. That pump is the bottom of a curve that will have climbed again by morning. Composition shifts across the day too, with different fat and hormone levels at 2am than at noon.

It also explains evening cluster feeding, which arrives at exactly the hour your breasts feel emptiest and reads like proof you have run out. Frequent feeding in the evening is how a newborn drives prolactin up and books tomorrow's supply. Exhausting, but working as intended.

The practical version: stop judging yourself by the evening pump. Nappies and weight gain tell you what you need to know.

The monthly dip

Almost nobody warns women about this one, and it blindsides the ones it hits.

When your period returns, and often a few days before it does, many women notice a real drop in supply and a baby who fusses at the breast. The usual explanation is the shift in oestrogen and progesterone around ovulation and menstruation, with a fall in blood calcium during the luteal phase. It is short-lived, and supply typically recovers within a few days of bleeding starting.

The confusing part is that it happens even when you are feeding constantly, because it is being driven by your cycle rather than by anything you did or did not do at the breast. Expecting it takes most of the fear out of it. Some women find that keeping calcium and magnesium up across the month softens the dip, though the evidence there is more traditional than proven.

The milestone dips

These are tied to your baby changing rather than to you, and they are the most misread of the lot.

Around three weeks, six weeks, three months and again near six months, babies feed as though they have never eaten. This is your baby placing an order, feeding constantly for a day or two to reset the thermostat upwards. Reach for a bottle to get through it and the order never lands, so supply stays where it was rather than climbing. That is the mechanism behind an enormous number of well-meaning top-up bottles that ended a breastfeeding relationship earlier than anyone intended.

Teething and illness work the other way. A baby in pain or congested feeds less, less milk is removed, and supply follows within days. It rebounds once they are comfortable, provided you keep offering and keep the breast drained, even if that means a short pump you resent.

Starting solids brings a gentle down-regulation from around six months as food comes in. That decline is correct. The risk is reading it as a cliff and weaning faster than you meant to.

The circumstantial dips

This is the category you have the most control over, which is either encouraging or more pressure depending on the day.

Going back to work. A pump does not empty a breast the way a baby does. Babies combine suction and compression, and their saliva even signals the breast to adjust what it makes. No machine replicates that. So output falls, and a mother reads it as her supply collapsing when the tool is simply underperforming the baby. Pump output is a poor proxy for production.

Stress and no sleep. The distinction here matters enormously. Acute stress rarely destroys the milk you have made. It interferes with getting it out. Cortisol blunts oxytocin, so on a tense, running-late morning the milk is there but slow to release, which feels identical to low supply from the outside. Grinding, months-long stress and severe sleep deprivation can eventually reach production itself, but the panic-day version is a let-down problem.

Under-eating and dehydration. Lactation is metabolically expensive. Postpartum crash diets, the day you forgot to eat, the week you were too underwater to drink water. All of it pulls supply down because the system is short of raw materials, and it hides behind a lot of what gets called low supply.

What protects you across all three is unglamorous. Feed or pump on a rhythm your breasts can rely on. Take thirty seconds of warmth and slow breathing before you start, particularly with a pump. Eat properly, drink more than you think.

Herbs, foods and medications

Some dips have a cause sitting in the kitchen cupboard or the medicine cabinet, and this is where women most often blame their bodies for something a tablet did.

A handful of botanicals have been used for centuries to dry milk up, which makes them useful at weaning and unhelpful before it. Sage is the best known. Peppermint, parsley, oregano, lemon balm, yarrow and jasmine sit in the same traditional category.

Dose is what matters, and this is where the internet frightens people for no reason. Parsley on your potatoes will not affect your supply. A mint in your handbag will not affect your supply. The concentrated end is different: strong sage tea drunk repeatedly through the day, peppermint essential oil, high-strength tinctures and extracts. Culinary amounts and medicinal amounts are not the same thing.

Vitex, or chasteberry, deserves its own line because it appears in so many women's hormone supplements. It acts directly on prolactin, and the direction of that effect is dose-dependent and still contested. If you are breastfeeding and taking a hormone blend containing it, you are taking something that acts on the hormone your supply runs on.

On medications, pseudoephedrine is the one every breastfeeding woman should know. The decongestant in many over-the-counter cold and flu tablets, a single dose measurably reduced milk production in a controlled study, which is why so many mothers report an unexplained drop the week they had a cold. It was the tablet.

Alongside it: combined oestrogen contraception, which is why progestogen-only options are the standard recommendation while breastfeeding. Ergot-derived drugs such as cabergoline and bromocriptine, prescribed precisely because they suppress lactation. Older sedating antihistamines. High-dose diuretics. Testosterone. Smoking and vaping both track with lower supply and shorter breastfeeding duration.

Alcohol behaves differently to how most people assume. It does not reduce the milk you have made, it blunts oxytocin and gets in the way of let-down, so less comes out in the moment. The visible outcome is the same and the fix is not pumping harder.

Before you accept a new prescription or reach for a cold and flu tablet, say out loud that you are breastfeeding and ask whether it affects supply. Pharmacists tend to be better on this than anyone. If a dip started within days of a new medication, you have probably found your answer.

When it is medical

Most supply articles skip this part, which is exactly why the women who need it most end up reading five of them and still feeling blamed. If you have done everything right and the milk never came, you deserve an investigation rather than another instruction to feed more often.

Thyroid is the most common treatable cause and the most missed. Both underactive and overactive thyroid can suppress production, and postpartum thyroiditis affects a meaningful percentage of women in the first year, routinely mistaken for ordinary new-mother exhaustion. Hashimoto's sits here too. If supply is low and you are also cold, flat, losing hair and shattered beyond what a newborn explains, ask for thyroid bloods.

Retained placenta. Even a small fragment keeps progesterone high, and high progesterone blocks the hormonal switch that brings milk in. It shows up as milk that never properly arrived, often alongside ongoing bleeding. It needs a doctor and it is fixable.

Severe postpartum haemorrhage is associated with delayed and reduced production. In rare cases where the pituitary is damaged, a condition called Sheehan's syndrome, prolactin production itself is affected.

Anaemia and iron deficiency. Common, under-tested, consistently linked with lower supply, and easy to check.

PCOS and insulin resistance. The relationship runs both ways. Some women with PCOS have abundant milk, others have delayed or insufficient supply. Insulin plays a direct role in milk synthesis, which is the working explanation for why insulin-resistant conditions and gestational diabetes show up alongside delayed lactogenesis.

Insufficient glandular tissue is the true primary low supply. Markers can include widely spaced, tubular or markedly asymmetric breasts, and an absence of breast changes during pregnancy. It is rare, it is not caused by anything you did, and no amount of extra feeding fixes it. Naming it accurately is kinder than letting a woman believe she failed at something that was never physiologically available to her.

Previous breast surgery. Reduction, augmentation or anything involving the areola can sever ducts or nerves. Plenty of women breastfeed successfully afterwards, often alongside supplementation, but it belongs on the list of real physical factors rather than in the pile of things attributed to mindset.

Acute illness. A fever, a stomach bug or a bad flu will usually dent supply for a few days, mostly through dehydration and reduced feeding. Mastitis often causes a short drop in the affected breast. Both recover as you do.

On autoimmune conditions. Women with lupus, rheumatoid arthritis, coeliac disease or Sjögren's often ask whether the condition itself lowers supply. The honest answer is that direct evidence is thin. What is well established are the routes around it: thyroid involvement, the medications used to control flares, anaemia, and the fatigue of a chronic illness colliding with a newborn. None of that predicts failure. It does mean getting thyroid and iron checked early, and having your medications reviewed against a proper lactation database rather than a patient information leaflet.

What actually moves the needle

The real levers are few and mostly boring. Remove milk often and effectively. Lower the stakes around let-down. Feed the mother, because a depleted body deprioritises milk. Drink, because you cannot make a fluid out of nothing.

That last pair is the thinking behind the Breastfeeding Herbal Blend I formulated after my own worst months. Fennel, moringa, oat straw and nettle, botanicals long used in lactation traditions, in a hot infusion because the format pulls the most out of the plant while putting fluid back into you. It will not fix any of the dips above, and most of them do not need fixing. It is a warm ritual for the woman in the middle of them, which on the bad days is not nothing.

Looking back

I can name exactly what was happening that afternoon now. It was 4pm and my prolactin was at its daily floor. I had eaten almost nothing since breakfast. And I was assessing a resilient system by its worst hour of the day, using a machine that was never going to match my daughter.

Nothing had failed. I had just never been told any of this, which is the part that still bothers me, because I know how many women stop before they find out.

When a dip is worth a call

Most dips resolve on their own. Speak to your GP, health visitor or a lactation consultant if your baby is not producing enough wet nappies, is not gaining weight or is unusually lethargic, if a drop is sudden and severe, or if feeding hurts. Those need real support, and getting it early protects both of you.

References

1. Academy of Breastfeeding Medicine, Clinical Protocols on supplementation and insufficient milk supply.

2. Wilde CJ, et al. Autocrine regulation of milk secretion by a protein in milk (Feedback Inhibitor of Lactation). Biochem J, 1995.

3. Italianer MF, et al. Circadian variation in human milk composition. Nutrients, 2020.

4. Kent JC. How breastfeeding works. J Midwifery Womens Health, 2007.

5. Neville MC, et al. Lactogenesis and the physiology of milk production. J Nutr, 2001.

6. Aljazaf K, et al. Pseudoephedrine: effects on milk production in women. Br J Clin Pharmacol, 2003.

7. Stuebe AM, et al. Failed lactation and perinatal depression: common problems with shared neuroendocrine mechanisms. J Womens Health, 2012.

8. Nommsen-Rivers LA. Does insulin explain the relation between maternal obesity and poor lactation outcomes? Adv Nutr, 2016.

9. Huggins K, Petok E, Mireles O. Markers of lactation insufficiency: a study of 34 mothers. Current Issues in Clinical Lactation, 2000.

10. Stagnaro-Green A. Postpartum thyroiditis. Best Pract Res Clin Endocrinol Metab, 2004.

11. LactMed (Drugs and Lactation Database), National Library of Medicine.

ABOUT HILARY

Hilary is the Co-Founder of The SABI, a Holistic Nutritionist, natural, whole foods Chef, product developer and advocate for women getting to know their bodies, cycles and selves better. Born in Los Angeles, California and raised in Baja California, Mexico, she now lives in Los Cabos with her partner Kees, their curly-tailed rescue dog from Curaçao, Flint, and her rainbow babies Paloma and Bea.

HORMONAL & PROUD

The SABI was created to help women through the hardest moments of pregnancy, childbirth, postpartum and every stage that follows. We want to change the story around our hormones, from one of taboo, embarrassment and loneliness to one of awareness, and even pride.

More than a wellness brand, The SABI is a line of rituals, supportive tools and functional herbal remedies, tested by hundreds of years of traditional medicine and now backed by modern science. It was conceived by women who have lived the joys and the deeper costs of bringing a child into the world, of a heavy or difficult period, of miscarriage and trouble conceiving.

Consider this an invitation to know your body and its cycles, to learn to work with them at any stage of life, and to know that support exists. Look for the right sources, know there is help, and know that you are not on your own.

DISCLAIMER

The SABI blog and articles are not meant to instruct or advise on medical or health conditions, but to inform. The information and opinions presented here do not substitute professional medical advice or consultations with healthcare professionals for your unique situation.