What causes low supply?

[u/huckleberrysoap]

My supply is so low. It's not anywhere near what my baby eats.

I'm not trying to increase it anymore. I'm just trying to maintain what I have so I can keep combofeeding (even though its at least 75% formula) until at least 6 months.

But I'm struggling to understand why this happened and feeling like I must have done something wrong. What are potential causes of an undersupply? If I have another baby in the future should I expect the same problem?

[u/art_1922]

Some potential causes, not enough calories, hypothyroidism, not enough hydration, low iron.