A night with writer's block - 2am Wednesday morning

I am in the middle of writing two fictional novels, although one has been temporarily put on hold. The one I am currently working diligently on is a mystery/romance story with, hopefully, a suspenseful twist. One of my characters is a mother who is slowly poisoning her 12 year old son. I need some ideas on how the woman would go about this over a period of several months to a year, only making the child sick enough to require hospitalization without actually killing him. I've been doing research, unfortunately Wikipedia is down right now, and case studies of actual crimes tend not to divulge every detail. I want my writing to be as realistic as possible. Please keep in mind folks, this is totally fictional, for the purpose of my book. I do not wish to actually make anyone ill or commit murder. If anyone has any ideas for me, feel free to respond.