The Role of Hydration in Supporting Breastfeeding and Milk Production

By Anna Cave-Bigley

When I was breastfeeding, the thirst hit me like a wave,  sudden, fierce, impossible to ignore. Every feed, especially at night, left me gulping water as though I’d crossed a desert. At first, I thought it was just fatigue or nerves. But later I learned: that desperate thirst is built into biology.

Breastmilk is about 87–90% water (NIH Bookshelf), and every feed pulls fluids, electrolytes, and nutrients directly from a mother’s body. Producing milk requires more water than almost any other metabolic function in a woman’s life. And yet, hydration in breastfeeding is one of the most misunderstood and overlooked factors in maternal care.

So what exactly happens when we’re hydrated (or not) while breastfeeding, how does it affect supply, and why isn’t just “drink more water” enough?

The Physiology: How Fluids Become Milk

Breastmilk is produced in the alveoli, tiny sacs inside the breast lined with lactocytes (milk-making cells). These cells pull water and nutrients directly from maternal plasma (the liquid part of blood). That means maternal hydration status directly influences milk composition and flow.

• Water in = milk out: when plasma volume dips (even mildly), the body prioritises vital organs first, not milk production. This is why dehydration often feels like “slower let-down” or “lighter supply.”
  

• Electrolytes: sodium, potassium, and chloride shift into milk in tightly controlled ratios. Overhydration without electrolytes can dilute these balances, sometimes making milk less palatable to the baby.
  

• Hormonal triggers: oxytocin and prolactin release depend on maternal fluid balance. Stress from dehydration spikes cortisol, which can interfere with oxytocin let-down reflex.
  

This is why mothers often feel a “rush of thirst” the moment their baby latches, the hypothalamus triggers it alongside oxytocin release, a biological nudge to drink while feeding.

How Much Do Breastfeeding Mothers Actually Need?

Here’s where the research gets tricky. There’s no single “perfect number.” Needs vary by body size, climate, activity level, and even infant demand.

• The Institute of Medicine recommends lactating women aim for an extra ~700 ml/day above normal requirements, about three cups more (NIH Bookshelf).
  

• In practice, that brings the total to 3 litres/day on average, though some women may need more in hot climates or with multiple feeding sessions.
  

• A study in Applied Physiology, Nutrition, and Metabolism found that inadequate fluid intake in lactating mothers correlated with higher fatigue scores and perceived low supply.
  

What matters most isn’t hitting a rigid number but steady intake spread across the day. Gulping a litre at once won’t do what consistent hydration does for milk flow.

It’s Not Just About Water

Hydration science during lactation is more nuanced than “eight glasses a day.”

1. Plain Water
    Essential, but insufficient on its own. Rapid overconsumption can dilute electrolytes and increase urinary output without meaningfully improving milk supply.
   

2. Electrolyte Support
    Sodium and potassium losses rise postpartum due to sweating, blood loss, and milk production. Mineral-rich broths or light electrolyte solutions (ideally low in added sugar) can stabilise plasma volume better than water alone.
   

3. Hydrating Foods
   Watermelon, cucumber, oranges, pears, and soups provide fluids with natural sugars, vitamins, and minerals. Research shows that fluid-rich foods may be better retained in plasma than plain water (European Journal of Clinical Nutrition).
   

4. Herbal Infusions
   These do double duty. Our Breastfeeding Herbata combines fennel, moringa, nettle, oat straw, tulsi, and vervain. Not only do they hydrate, but fennel and moringa have been linked to improved lactation outcomes. 

What Happens When You’re Not Hydrated

Even mild dehydration shows up fast in a breastfeeding mother:

• Sluggish let-down (oxytocin reflex delayed).
  

• Fatigue and headaches (reduced plasma volume).
  

• Perceived low supply (though often reversible once hydrated).
  

• Irritability and poor mood regulation, hydration status directly influences cortisol and serotonin pathways.
  

Chronic underhydration doesn’t just affect supply, it prolongs postpartum recovery, worsens constipation, and can even affect sleep quality, already fragile in this season.

Hydration as Ritual, Not Obligation

Here’s the truth: telling a mother “drink more water” isn’t helpful. She’s already juggling feeds, nappies, her own recovery. What works is anchoring hydration into rhythm:

• A glass of water with every feed.
  

• Herbal infusions at night, hydration plus calming adaptogens like tulsi.
  

• Broths or soups at lunch to replenish electrolytes.
  

• A beautiful, ever-full bottle by the bed, because night thirst is inevitable.
  

When I reframed hydration as a way of caring for myself, not another chore, everything changed. My supply steadied, my headaches eased, and I felt just a little more human in those bleary weeks.

HORMONAL & PROUD

Created as a brand to help women navigate the toughest moments in pregnancy, childbirth, postpartum — and practically every stage of life –– The SABI is changing the narrative around our hormones from one of taboo, embarrassment, and loneliness to awareness and even, pride. As more than a wellness brand, The SABI offers a carefully-crafted line of products to carry you through your hormonal journey, including rituals, supportive tools, and ancient herbal remedies that have been tested time and time again by women and now come backed by medicine. The SABI is a blend of science and nature conceived by women who have experienced the joys and deep struggles of bringing a child into the world, the pains of a heavy, difficult period, miscarriage, and difficulty conceiving.

We invite you to get to know your body and its cycles better –– to really understand what is going on inside. Learn to use your hormones to your advantage no matter your stage of life, and know that you can support and balance your hormone levels. We are here to help with the information, understanding and natural tools to support your body and the emotional process along with it.

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.

References

1. Neville MC, et al. Nutritional requirements during lactation. NIH Bookshelf.
   
   

2. Institute of Medicine. Nutrition During Lactation. National Academies Press.
   
   

3. La Leche League International. How much should I drink while breastfeeding?.
   
   

4. Heinrichs M, et al. Oxytocin, stress, and social behaviour. Front Neuroendocrinol. 2016.
   
   

Ortiz-Andrellucchi A, et al. Water, beverages, and hydration status. Eur J Clin Nutr. 2008