Dear patient
Low plt count is called as thrombocytopenia
Normal plt count is 150,000 to 450,000/cu mm
Platelet count > 60,000 No bleeding
Plt count 30,000-60,000 leads to Bleeding with trauma
Plt count < 30,000 leads to Spontaneous bleed
Next Steps
if your father's hb and WBC count are abnormal go for BONE MARROW EXAMINATION
if your father 's hb and WBC count are normal go for PERIPHERAL BLOOD SMEAR and that will tell you about the cause (eg drug induced thrombocytopenia, infection induced thrombocytopenia ,or microangiopathic heamolytic anemia )
please connect if further queries