You might have noticed that the amount of milk that you pump varies over the course of a day. Why is this, and when is your milk supply the highest? Here’s what you need to know.
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Are milk supply fluctuations during the day normal?
Yes. Most people that pump breast milk exclusively note that their milk supply tends to be higher during some parts of the day, and lower at others.
For example, I would pump the highest volume in the middle of the night and first thing in the morning. The amount I pumped would gradually start to fall after that, with the lowest output being in the late afternoon or early evening.
Here’s a visual example of how my output would vary over 24 hours:
Your pattern might not be the same as mine, but this is just to illustrate how output can fluctuate throughout the day.
Why does milk production vary over the course of a day?
One theory is that these fluctuations are due to prolactin levels.
Prolactin is the hormone that is primarily responsible for milk production. Prolactin levels follow a circadian rhythm, with the highest values at night.
One study measured prolactin levels in 20 lactating women around the clock and found:
The circadian rhythm of PRL persisted throughout lactation as manifested by: (1) significantly higher mean nighttime than daytime PRL levels in the whole sample, despite higher daytime nursing durations; (2) the distribution of zenith levels which most frequently occur between 23.00 and 07.00 h, when nursing duration is lowest, and which are almost absent between 07.00 and 23.00 h, when nursing duration is highest, and of nadir levels, which have an opposite pattern.
When is milk supply highest?
While the exact time that prolactin levels peak seems to differ from person to person, it most often occurs somewhere between 11 pm and 7 am.
High prolactin levels at these times could lead to higher levels of milk production at these times. This means that milk supply would typically be the highest late at night to the early morning.
Why do I have low milk supply in the evenings?
Many people notice that their baby frequently cluster feeds in the early evenings. (Exclusive pumpers may also notice that they pump less at this time of day.)
Does this mean you have low milk supply?
No, not necessarily – for two reasons.
One, some babies may eat more in the pre-bedtime timeframe to “tank up” for the night.
Two, your prolactin levels may be lower at this time of day, meaning you might produce less milk then – but that doesn’t mean your milk supply is low overall.
Does this mean that you always need to pump at night to maintain your supply?
If you’re exclusively pumping, it’s a good idea to pump at least once a night for the first three months or so until your supply regulates.
After that, many exclusive pumpers are able to stop pumping at night without a decrease in the total amount pumped over 24 hours. However, some people do see a decrease after dropping this session.
If you’re nursing, I would nurse on demand and sleep when your baby sleeps.
Do you have any questions about how milk supply fluctuates or when milk supply is highest? Ask them in the comments!References
- Stern JM, Reichlin S. Prolactin circadian rhythm persists throughout lactation in women. Neuroendocrinology. 1990 Jan;51(1):31-7. doi: 10.1159/000125312. PMID: 2106085. https://pubmed.ncbi.nlm.nih.gov/2106085/
- Karp, Harvey. “Cluster Feeding: What Is It? How Do I Do It?” https://www.happiestbaby.com/blogs/baby/cluster-feeding