When I have my med levels checked my Doctor always tells me to take mine at a certain time. That is so they know how much should be there and if I’m getting to much or not enough. Based on that level and side effects I’m having he will increase my medication or switch it.

Because of the four Phenytoin 100mg I take a day my veins have lessened in size, especially around my biceps tendon area so they have to take any blood from the back of my hand :(

I am not familiar with the medication you’re taking about. But for me, I take my medications as prescribed. And 12 hours apart. Most are this amount in the am, and that amount in the pm.
As for your bloodwork, your neurologist is probably checking levels of your medications and other things,,to see if they need to alter the amounts or put you on a different, medication to help lessen your seizures.
And the best way for getting this information is bloodwork and talking with you. If you are not comfortable, and/or question how you’re epilepsy is being managed, talk with your doctor, or get another one.

The only time I would get my blood 🩸 drawn, when starting on a new medication . But my Dr. waits until I’m weaned off the medication the the new one will substitute. By the next visit to my Dr. , I will be on the new medication and fully off the other one. I would get my blood drawn Of the new med along with my previous meds I’m on. Then the doctor will know where my are levels are at and whether or not the med dosages need to be adjusted or not .

Phenobarbital has a very long half-life so it really doesn’t matter when it is drawn. Back in the day the doctor’s would try to get a trough level, meaning when the medication would be the lowest in your system. I am not too sure about my lamotragine and zonisamide. I do agree that your levels are affected by the time of day, when you last took your medications, what you ate, and when you last ate.