However, inherent problems exist with the PT. Due to the VKD factors´ significantly different half-lifes (above), the PT clotting time obtained early after initiation or dose change may mainly reflect the concentration of factor VII since FVII has the notably shortest half-life (about 4-8 hours). If the concentration of factor VII has little influence on the antithrombotic effect of VKA (see below), it is possible that unnecessary and too frequent dose adjustments are made based on the use of the PT. This, could potentially be harmful to the patient.