1/2 life of enzyme CK?

["guest@endurance.net" <guest@endurance.net>]

Kristi iluvdez@yahoo.com
Blood tests taken 70 hours after my horse produced dark urine 
showed a CK level of 2,000 (don't get me started on why there was
a delay in doing the test). Can you use 1/2 lifes to actually figure 
out how high it was initially, or only in theory? I hope you can't 
because my figures show that since CK has a 1/2 life of 6 hours,
the # would be astronomical!! Is there any way to figure out what
it was initially, or does it vary from horse to horse on the 
speed in which it drops? 

Kristi