Blood creatinine level. The blood creatinine level shows how well your kidneys are working. A high level may mean your kidneys are not working as they should. The amount of creatinine in the blood depends partly on the amount of muscle tissue you have.
Xanax is stronger. 0.5 mg of Xanax equals 10 mg of Valium. But Xanax is mostly effective for about 2 hours, then you may have to repeat the dose (and regular doses may cause addiction). Valium peak-level effects wear off after 1 hour, but it stays in blood longer, and continues working for about 12 hours.
Most benzo equivalency charts (not all of them agree) would tell you: 10 mg Valium = 2 mg Ativan = 1 mg Xanax = 0.5 mg Klonopin. I'd say most benzo charts are in error and overstate the potency of Klonopin, showing it to be twice as strong as it really is. I'm personally not a fan of Klonopin. I think it's so overrated, as it it's somehow magically better than other benzos.