I take 2 250mg tabs in the a.m. after breakfast. I think it took ~3wk for me to notice a difference. I'm guessing I am pretty deficient since I don't have any negative GI impact from taking 500mg a day. Make sure not to take it with calcium or any calcium rich foods/antacids/supplements or else it will compete with the mg.
I hope it works for you. You may also want to consider a sublingual B12 or just a good B complex.
Mom to two amazing DDs ('07 & '09) and a fur baby.
Gluten free since Nov '11 after non-celiac gluten sensitive diagnosis. Have had great improvement or total elimination of: migraines, bloating/distention, heartburn, cystic acne, canker sores, bleeding gums, eczema on elbows, dry skin and scalp, muscle cramps, PMS, hair loss, heart palpitations, fatigue. I'm amazed.