Hi. I wish I could help, but really don't know what to say. First, I would ask, have they determined what is causing the low platelet production? Secondly, it was my understanding that L-carnitine was used for cats who are deficient in this enzyme and it mostly causes heart and skeletal muscle health problems.
Hopefully someone else on this site has better knowledge in this area and can offer some insight. Hang in there until they do!