It's normal to have one produce more than the other. There was a study that said the majority of moms produce more on the right than the left. I happen to be opposite though.
I agree with PP. The same thing happened to me with DS. If you want to keep them more even, try to put baby on the lower performing breast first, then the other one in addition to extra pumping time/frequency-- but also know that you can feed from one. My supply tanked in my left after 9 months when DS showed a really strong preference for the right (it let down faster). I didn't have time to pump the left extra, so by the time he was 14 months, a 20min pump would result in 50ml left side, 350-400ml right side. The difference was ridiculous, but both sides continued to produce milk.
Lefty produces 1/2 to 2/3 of righty but at 13 weeks, having tried everything to catch Lefty up like pumping extra and always feeding from that side first, I've accepted Lefty does what she can and that's the end of it. Nothing has worked to even it out.
My right side also produces more most of the time but LO prefers the left side for feeding. I think the let down on the right may be too strong or he just prefers the position. I'm going back to work soon so I'm thinking I'll feed him then pump the right to even myself out and start up my freezer supply
My left boob is HUGE and produces so much milk. (5oz)My right one barely gives me anything.(1.5oz) There is a physical difference too. My bra doesn't fit right and you can tell the one is bigger if I am not wearing a bra. I am hoping that it goes back to normal once I am done breastfeeding.
My breast were uneven before pregnancy, all throughout, and continue to be now, I will almost always get more from the larger breast. Weird how our bodies work.
Re: Uneven supply