1mg Finasteride daily does NOT reduce serum DHT -- should I up dosage? (photos)

You should not be managing your medication.  Hopefully you have found a board certified dermatologist who specializes in treating hair loss.  You should schedule a follow up visit with your physician to discuss your results (who ordered the blood test?) and your options.  I would not recommend playing around with your medication.  The doctor who prescribed it is responsible and should be involved with the planning/management. For some men  a stronger medication called Avodart works better to grow hair.  Many men, however, find that the level of sexual side effects is higher as well.  

no need to increase the intake of drug because increasing the dosage will not change the effect of finasteride. 

It’s a bit more complicated than this and you may want to see a physician to review. If your DHT was once in the many hundreds and is now 89, this would be a marked reduction for which further dosing of finasteride would have little benefit. One must also consider many other factors here. DHT overall is quite an unreliable measurement.