Slow caffeine metabolism

Is extremely slow caffeine metabolism an indicator for serious liver problems?  A decaf coffee at 6am gives me severe insomnia.

I've studied the liver challenge tests but it's not obvious if I should take one.

[mikesimon]

I have never heard anything like that - "slow caffeine metabolism an indicator for serious liver problems".
Regardless a "decaf coffee" should not contain very much, if any, caffeine and therefore should not be the cause of insomnia or suggest a slow caffeine metabolism.
If you're worried about your liver maybe you should get some blood tests.

Good luck,
Mike