Oh yes Catherine, I do realize that we're talking about a 3 year old. I mention adult thresholds because levels for children are seldom, if ever established. Generally with children, depending on age and body weight, figure doses at 25-50% of the adult dose. With a water soluble vitamin, doses can be more towards the 50% range because they wash out of the body so quickly.
For Leonardo, though I would suggest daily folic acid, but the dose of 2000 that I mention is in relation to adults. The dose recommended by the doctors of 500 is good but I would suggest daily because his Hb has been dropping so low.