Menu Close

Lactose Overload: What You Need to Know

Mother holding crying newborn infant.

In an earlier post, I talked about lactose intolerance. But now, I want to explain the implications for a related condition, lactose overload.

What is lactose overload?

In the simplest terms, lactose overload is an imbalance between the amount of carbohydrate (lactose) to the protein and fat components of the milk.

True, the amount of lactose is proportionally dominant in human milk. But in this situation, the amount of lactose is much greater than the amount of fat.

It’s also referred to as functional lactase insufficiency.

Possible causes of lactose overload?

Honestly, I don’t know why (or even if) it happens in older infants. But in young infants (meaning, those who are less than 6 months old), it’s not uncommon.


Don’t assume this is a breastfeeding thing. It isn’t. It can and does happen in formula fed infants.

Lactose overload can happen when the baby can’t control the flow of the fluid in the bottle, or the parent is “force-feeding.” That’s hard to explain, but if you’ve ever seen it, you know what I mean. (And in my estimation, this is an early invitation to the clean plate club that many adults belong to!)

If formula fed infants can’t control the flow of milk, they can experience lactose overload because they’re just plain taking in too much formula. And a major strategy for overcoming that is paced bottle-feeding. (That technique is the brainchild of expert IBCLC Dee Kassing.)

Hindmilk/foremilk imbalances

Hindmilk foremilk imbalances can happen when the mother has an oversupply of milk. It can also happen with switch nursing.

Signs and symptoms of lactose overload

Young infants generally have gastrointestinal (GI) signs and symptoms. Typically, these include:

Excessive spit-up

Here, I’m talking about more than just a wet burp. The baby regurgitates a substantial amount of milk. In fact, they might give a milk “shower” to whoever is holding them!


Sure, babies cry. But they usually don’t cry after a feeding. Crying that’s accompanied by other GI symptoms after the feeding is over, might be an indication of lactose overload.

Watery, explosive stools

To me, this is a tell-tale sign. Caregivers are likely to observe a large, watery stools that leak out of the side of the diaper.

Bright green, frothy stools

It’s certainly possible that babies have green stools for a different reason. But in lactose overload situations, the stools are a very bright green (think shamrock-green here) with a frothy appearance. Not surprisingly, these kids will have a diaper rash.

Hungry within an hour or two of the last feeding

No doubt, some babies want to nurse an hour after they’ve had a good feeding. That’s because babies nurse for reasons other than hunger. But in context, this “asking to nurse” looks different.

Here’s the context: These babies have all the other GI signs and symptoms. They’re acting hungry because of the gas that’s building up in their systems. They may want to nurse to be soothed, but nursing doesn’t help much, or doesn’t help for very long.

Rapid weight gain

Ah yes. All of us are eager to see weight gains. Weight gains are good, right? Well, maybe not.

The rapid weight gain occurs because the milk is so sugary. Go ahead; try this for yourself. Put a handful of sugar into a bowl. Add a larger amount of water. See what happens? The water is sucked into the sugar.  

These babies are gaining weight, but it’s water weight. Thankfully, on the whole, they’re healthy.

But these signs and symptoms aren’t just about the baby. The mother has signs and symptoms, too.

A forceful or overactive let-down

This is hard to explain, but if you ever see it, there will be no doubt in your mind. The baby has several short sucks and then suddenly, pulls away from the breast, gagging, and swallowing air.

Moms often describe this as “looks like the baby is drowning.” Or, “my let-down was momentarily painful”, or “like a hose sprayer.”

Lots of leaking

It’s almost as both mom and baby are trying to turn off the “hose” but are unable to do so. Having lots of soaked breast pads is a good clue.  

So, let’s try to briefly recap what’s going on in cases of lactose overload. 

  • First, there is an excessive consumption of lactose (for one reason or another).
  • Then, these sugary feedings result in more GI microorganisms, which leads to …
  • The baby has GI discomfort, explosive green stools, and all of the other GI signs and symptoms.

Strategies for Lactose Overload

We could probably talk more about this, but here are some simple strategies to try:

  • Positioning. Holding the baby upright
  • Burping. More frequent burping
  • Expressing a little from the breast before feeding or allowing the baby to suckle just a little and once there’s a milk-ejection reflex, let the milk just splash onto a cloth, then resume. (This is far and away my favorite strategy!)
  • Check for overactive milk-ejection reflex. This is not always a concurrent problem, but it can be, so just beware.

What about resolution and follow up?

Follow-up visits should be done within about 5-7 days. Priorities include:

  • Identifying patterns of what’s going on in both mom and baby. This includes number of feedings, number and characteristics of stools, degree of spit-up, and any of the other signs and symptoms mentioned above.
  • Trying different strategies if the current strategies aren’t working or aren’t working well enough.
  • Identifying patterns: Number of stools,

When you have a clearer understanding of what lactose overload is, along with its possible causes, you can generate some strategies to overcome the problem, and make sure there’s a good follow-up plan in place.

As my long-time friend and colleague, Debi Bocar RN IBCLC PhD, told me more nearly four decades ago, most breastfeeding problems are transient, and solvable.

What symptoms of overload have you seen? What are your strategies for overcoming lactose overload?

Share this


  1. Kim Cook

    What about a baby that can’t tolerate mom having any dairy? I have a client that her baby would cry and cry when mom has dairy. Baby had several tests and a hospital admission for a twisted small intestine that doctors could not agree about. She went to a Children’s Hospital. It appears that baby can not tolerate any secondary milk enzymes coming through mom’s milk. She spit up a lot also. She is now 9 months old and can tolerate a small amount of mom having dairy, i.e. cheese.

    • Marie Biancuzzo

      Kim, thank you for bringing this up. I’m not clear on exactly what your question is, and I’m not licensed to diagnose (and I’m thousands of miles away and I haven’t seen the clients!) But there are a few things that jump out at me with your story. Sometimes, these conditions get diagnosed as “lactose intolerance” when they aren’t! Sometimes, it’s an anatomical anomaly, as you just mentioned (a “twisted” small intestine).

      But sometimes, it’s a cow’s milk allergy, and has absolutely nothing to do with lactose intolerance.

      Cow’s milk protein allergy is a problem of protein. Lactose intolerance is a problem of lactose, a carbohydrate! The former is an allergic reaction to a macronutrient; the latter is an inability to correctly metabolize a macronutrient. Very different.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.