Yes, fenugreek has been used for centuries to increase milk supply in breastfeeding mothers (adoptive or not). You can take this herb by mouth (in capsule, powder, seed, tincture, or tea form), along with frequent pumping and/or nursing, to help your body produce more milk.
The usual dosage is about 1200 to 2400 mg, taken three times each day. If you've already begun to lactate, you may see an increase in your production within 24 to 72 hours of taking the herb. (Some moms don't see a result for two weeks or so.) You'll know you’re taking enough when your pee starts to smell like maple syrup. (Yes, really.)
Use fenugreek with caution if you have a history of diabetes or hypoglycemia, asthma, abnormal menstrual cycles, peanut or chickpea allergies, migraines, blood pressure problems, or heart disease. And, of course, always discuss any supplements — herbal or not — with your doc.