Fenugreek has been proven to be as effective as the drugs the doctor might prescribe to boost milk supply. However all galactagogues are only effective for 7-10 days, after that your body adjusts and is not so responsive to them.
In Ayurveda we recommend taking fenugreek as a tea to balance out it's dryness, not capsules. And also we mix it with other herbs to balance it's heating qualities. So here is my lactation tea recipe:
Mix 2 parts whole fennel seeds with 1 part whole fenugreek seeds. Add 1/2 teaspoon to 1 Litre of water and sip warm throughout the day. You can make it up in a thermos in the morning and keep it by your feeding chair.
You can buy organic spices from here if you don't already have them in your cupboard.
In the longer term you need to work on boosting your oxytocin levels to promote strong flow of milk. Oxytocin is boosted by doing anything that you love. For example when you breastfeed devote that time to gazing into your baby's eyes, stroking your baby's hair and singing your baby a song. Watch movies that make you laugh. Have a massage. Enjoy some sunshine or fresh air. Have a bath. Just take some time out for you.
This recipe is taken from my book "Nourishing Newborn Mothers - Recipes to heal your mind, body and soul after childbirth"