Dutasteride component of the medicine silofast D will reduce the serum PSA when taken over 6 months. Don't be concerned with it , even if it drops below the range. For the purpose of correction in people getting dutasteride over 6 months we multiply the values of serum PSA with a corrective factor( which is duration dependant) to get the original value.
Next Steps
don't get concerned with the values if it's below the permissible range and consult a urologist for proper evaluation and management.