Keppra and increase/change in seizures

Our son has myoclonic absence seizures.   He was diagnoised at age 6 and is now 19.  He has failed 9 medications over the last 13 years.

His Dr. asked us to retry Keppra 4 weeks ago.  He is very sensative to medications so he started him off at 500mgXR.  For 2 days there was no seizures.  But by day 3 they slowly returned.  They then increased to 750mgXR,  we had good days and bad,then he had a grand mal in his sleep.  Dr. insist that the drug is too low and had us increase to 500mgXR 2x per day.  Hoping to level the drug out in his system.  Since this change he is having longer, deeper and more frequent absence seizures with more frequent myoclonic movement.  His Dr. wants to increase the dose to 1000mgXr at night. and still the 500mgxr in the morning for a total of 1500mg. per day. He says for a 140lb 19 year old this is still a low dose.

We are worried as we read that if seizures change or increase be concerned.  His Dr. doesn't beleive this is due to the Keppra.

Our son also is complaining of peeing alot.  He gets up 1-2 times per night as well as peeing all day.

Just curious if anyone else has had this experience or can shed some light.  The Dr. says it would be a shame to stop the drug before we even get to a reasonable dose.  I asked for a blood level test and kidney function test and he says not needed.

Laurie