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.
Second, Valium is low in potency relative to most other benzodiazepines and comes in tablets of 2mg, 5mg and 10mg. As a practical matter, you can make cuts as small as 0.5mg. This is the equivalent of somewhere between 1/20th and 1/40th mg of Xanax or Klonopin.