Breastfeeding Hormones: what’s really happening in your body when you feed your baby

Breastfeeding gets called "natural" a lot. And sure — but so is a thunderstorm, and that doesn't mean it's simple.

The biology behind feeding your baby is genuinely fascinating, and honestly, nobody talks about it enough. Because once you understand what your hormones are actually doing, so much of what you're feeling starts to make sense. The exhaustion. The sudden tears mid-feed. The way you could eat an entire fridge and still feel empty. That's not you being dramatic. That's your body doing an enormous amount of work.

These shifts are driven by breastfeeding hormones like prolactin and oxytocin, which control milk production, let-down, and even your mood.

Let's get into it.

The two hormones running the show

Most of the day-to-day magic of breastfeeding comes down to two: prolactin and oxytocin.

Prolactin is the one telling your body to make milk. It rises during pregnancy, then once you give birth and the placenta is delivered — taking a big drop in progesterone with it — prolactin finally gets to do its thing. Here's the part that actually matters for early days: every time milk is removed, prolactin rises again. Feed more, signal more. It's pure supply and demand.

Prolactin is also probably why you feel like a sleepy, soft-focused version of yourself right now. That foggy, "I could genuinely fall asleep standing up" feeling? Prolactin. It's not a character flaw. It's a hormone.

Oxytocin is the one that moves the milk — the let-down reflex. And this one is wildlysensitive to your environment. It releases when your baby latches, yes. But also when you hear your baby cry, when someone holds your hand, when you feel safe and calm and not like you're being watched and graded. Stress, pain, feeling judged? Oxytocin goes quiet. Which is why breastfeeding can feel completely effortless in one moment and totally impossible in the next — same body, different nervous system state. Oxytocin is also why you might get hit with a wave of love (or unexpected tears) out of nowhere during a feed. Completely normal. Completely hormonal.

What set the stage before any of this started

Behind the scenes, pregnancy was already doing prep work. Estrogen and progesterone shaped your breast tissue. Cortisol, insulin, growth hormone — all quietly involved in getting your body ready to make milk. Which is also why things like blood sugar, stress levels, and metabolic health can play a real role in supply. It was never about effort. It was always about biology happening inside a very human body, in very real circumstances.

Your body is feeding a baby and healing at the same time

This part doesn't get said enough: lactation is a whole-body experience. Your appetite hormones shift. Your hunger and thirst increase. Your energy is being rerouted — outward, toward milk production — while your body is also recovering from pregnancy and birth. Needing more food, more water, more rest, more support right now isn't weakness. It's just physiology.

Why "trying harder" is the wrong framing entirely

Because oxytocin runs on safety and not on willpower, your environment genuinely matters. Feeling rushed, isolated, or like you have to prove something makes breastfeeding harder at a biological level — not just an emotional one.

Feeling seen, supported, and guided makes it easier. Not because mindset is magic, but because your hormonal system actually responds to care. If it's been harder than you expected It doesn't mean your body is broken or that you're doing it wrong. It might mean your hormones are navigating real exhaustion and stress. It might mean your nervous system needs more safety before oxytocin can do its job. It might mean you need more support — not more effort.

At Clementina, we think understanding your body is part of taking care of it. Not to make feeding feel like a biology exam, but because clarity is so much kinder than self-blame. You're not failing. Your body is communicating. And we're here to help you listen.

References

Wambach, K., & Riordan, J. (Eds.). (2016). Breastfeeding and human lactation (5th ed.). Jones & Bartlett Learning. (Chapter: The breast and the physiology of lactation.)

World Health Organization. (2009). Infant and young child feeding: Model chapter for textbooks for medical students and allied health professionals (Section: The physiological basis of breastfeeding). World Health Organization. https://www.ncbi.nlm.nih.gov/books/NBK148970/