Do a ratio dude:
12.2 19.5
------- = ------
200 x
Solve, and you get that x is approx equal to 320 mg.
Blood urea nitrogen (BUN) and creatinine tests can be used together to find the BUN-to-creatinine ratio (BUN:creatinine). A BUN-to-creatinine ratio can help your doctor check for problems, such as dehydration, that may cause abnormal BUN and creatinine levels.