For this telescope, the lenses are a concave convex (one side curved out and the other curved in) and a plano concave (one flat side and one side curved in). The plano concave lens is used as the eyepiece with the plano (flat) side facing the eye.
If kidney function begins to decline, BUN and creatinine rise. A normal creatinine depends on muscle mass and age. In general, a normal creatine is 0.5 to 1.2 milligrams per deciliter (mg/dL). A normal BUN is 7 to 20 mg/dL.
BUN (blood urea nitrogen) is a blood test to check kidney function. So is the serum creatinine test. When your doctor talks about BUN/creatinine levels or a BUN-to-creatinine ratio, he or she is referring to the two main blood tests that tell how well the kidneys are filtering waste products from your blood. The ratio of BUN to creatinine is normally in the range of 10:1 to 20:1.