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,
After spleen surgery,
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.

Hi and thanks for the query,
high platelets can temporally be high in some clinical scenarios not actually depicting presence of any serious disease. Moving to a high altitude zone might cause an increase in platelet count. Worn out platelets are destroyed or removed in the liver and spleen. Any dysfunction in these organs could lead to high platelet counts. Increased synthesis of platelets by the bone marrow, in a condition called polycythemia rubra vera, which is like a bone marrow tumoral condition is the commonest feared cause of raised platelet count. This usually deserves confirmation with a control of the platelet count a month later, usually with use of the sane laboratory, other blood tests like the erythrocyte sedimentation rate, complete blood counts, thin blood film and a bone marrow aspirate depending on the case. Persistence of high platelets depending on the case might deserve the opinion of a hematologist.
Thanks and best regards,
Luchuo, MD.