Results of the creatinine blood test are measured in milligrams per deciliter or micromoles per liter. The normal range for creatinine in the blood may be 0.84 to 1.21 milligrams per deciliter (74.3 to 107 micromoles per liter), although this can vary from lab to lab, between men and women, and by age. Since the amount of creatinine in the blood increases with muscle mass, men usually have higher creatinine levels than do women.
Generally, a high serum creatinine level means that your kidneys aren't working well. Your creatinine level may temporarily increase if you're dehydrated, have a low blood volume, eat a large amount of meat or take certain medications. The dietary supplement creatine can have the same effect.
If your serum creatinine level is higher than normal, your doctor may want to confirm the results with another blood or urine test. If kidney damage is a concern, it's important to control any conditions that may be contributing to the damage. It's especially important to manage your blood pressure, which often requires medication. You can't undo permanent kidney damage, but with appropriate treatment you may be able to prevent further damage.