Creatinine - assessment, reference ranges, elevated and decreased levels, dietary considerations
Tomasz Jankowski
2026-03-20
3 min. read
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A blood test provides us with valuable insights into our health condition. One of the key parameters assessed is the plasma creatinine level. What conclusions can be drawn from such a test, and what factors might cause deviations from the standard reference ranges?
Creatine
Creatine (from the Greek kreas, meaning meat) is a chemical compound that is formed by the degradation process of about 12% of creatine in muscles, so the overall plasma creatinine concentration depends on muscle mass, sex, and age.
Testing of creatinine
Creatine is excreted from the body with the urine and thus passes through the kidneys and is therefore perfectly tested in the study of the function of this organ. The day before the test is recommended to avoid excessive physical activity, and the last meal should be eaten at about 6:00 p.m.
Standard of creatinine
The reference values range from 53 to 115 μmol/l (0.6 to 1.3 mg%) depending on the previously mentioned muscle mass, sex and age of the subject.
Creatine is elevated
Creatine levels are elevated by damage to a large part of the nephron and decreased lumbar secretion. Haemolysis leads to a false elevation of the result. Other factors that increase creatine concentrations are ketone acid, creatine-containing supplements, and medicines such as cimetidine, acetylsalicylic acid, trimethoprim that inhibit the pulmonary production of creatinine.
Low creatinine
Reduced blood creatinine levels are rare. The causes of a decrease in concentration include reduced muscle mass. This is due to the relationship between the mass of this tissue and the amount of creatine produced from muscle creatinise. The decreise in concentration progresses with age and is the lowest in the elderly, so in this age group, despite low creatine levels, renal function may be impaired at the same time.
Creatine and diet
Diet can also have an effect on creatine levels. A significant effect on the level of the compound studied is a meat diet. In people who eat a large amount of meat that contains about 25g of creatine in 1 kg, creatinine levels can increase by as much as 30%. Similarly, a diet rich in meat results in a decreased plasma creatine level. A lower level is also associated with malnutrition or a low-protein diet that can lead to muscle loss.