I get a good chunk of my hits from moms looking to or havig trouble breastfeeding twins, and their google searches often imply that they're about ready to give up. Ex: breastfeeding twins is too hard, breasfeeding twins about to give up, breasfeeding preemie twins no success - and that's just today. I can understand that, because it's not at all easy to breastfeed multiples in the beginning, even if everything is going according to plan. If that's you, please check out the category I have for that purpose, because perhaps my experince, or the links I've posted there, will be helpful to you. I recently read a new twin mom's frustrated post about supply issues with twins, and thought I'd paraphrase my own reply here in case it's helpful to anyone.
Kellymom has some decent information on both breastfeeding multiples and on supply issues.
I think something even lactation consultants rarely seem to understand is that the situation of having more than one is particularly problematic with growth spurts. My intuition and own experience lead me to suspect that getting through growth spurts with twins is the second biggest issue that eventually leads to low supply (the first being not establishing a good supply in the beginning).
With one baby, the baby demands more during a growth spurt, and in a day or 2 your supply increases to meet the demand. Some fussiness is perfectly normal here; it’s part of the process. With twins, however, your actual supply needs to increase doubly, and while your body can most likely do that, it cannot do so twice as fast. What tends to happen then, is that the extra fussiness leads to doubts about supply, the doubts lead to more supplementation with formula, the supplementation leads to less stimulation, which, in turn, leads to not building the necessary supply. Which is to say, none of this means that your body is actually incapable of producing the milk. Some women have genuinely low supply, but this is an often misunderstood issue.
It’s a complex logistical problem though. Over the months, I came to learn that my boys get much more from breastfeeding than I can produce with a pump, so your supply may not be as bad as it seems. I know this is a lot to balance, but if you nurse on demand (at least during the day), have lots of skin-to-skin contact, and pump after every feeding you can manage to, you might find that you can get past the hump and keep breasfeeding even though you've been told you have low supply.
I couldn’t deal with the fussiness in the evenings when my supply was lowest, so I fed them each one bottle of expressed breast milk then, but always bf first, and I pumped after every feeding too. I had a weak suckler in the beginning, and he got much better after a couple of months.
To the exhausted, confused, hormonal and overwhelmed new twin mom reading this in the middle of a long night (as I would've been): whatever you decide, best of luck to you. You are doing a very hard thing, you’re doing your best, and that’s all anyone can ask of you.
*when I say "at least during the day", I'm not suggesting refusing an infant who wants to eat at night. I mean that when one woke, we woke the other too so we could be more likely to get at least a couple of hours of sleep in a row. For me, especially later in the game, the biggest dips in supply came when i was completely exhausted. It takes a ton of calories and energy to produce milk for twins, and I think the need for sleep needs to be dealt with even if it means trying to feed the babies together whenever possible. Neither baby ever seemes to mind being woken to eat in the slightest.