Hi thanks for your question.
There are 2 types of causes for increased platlet.
No 1;Primary where bone marrow
produce more platlet and cause is not known called as primary thrombocytosis
.This type is congenitally inherited that is pass from parents to childeren.
No 2;Secondary .In this platlet increase in response to many diseases in body.There is long list of diseases but most common are;
Cancer of gut, breast, lung ,ovary and lymphoma
Iron, deficiency anaemia
and hemolytic anaemia,
Inflammatory bowel diseases and some infective diseases.
There is no vitamen or drug which can decrease platlet.It has to be investigated and treated.
I would suggest yout consult a haematolgist who may be able to evaluate you for your increased platlet and may treat accordingly.
Hope this answers your question.