The microalbumin creatinine ratio (MACR) test is a simple urine test used to assess kidney health. It identifies early indicators of kidney damage, often before symptoms become apparent. This test provides valuable insights into the filtering function of the kidneys.
What is the Microalbumin Creatinine Ratio Test?
The MACR test measures two substances in a urine sample: albumin and creatinine. Albumin is a protein found in the blood that kidneys typically prevent from passing into the urine. If the kidneys are damaged, even slightly, they may allow small amounts of albumin to leak into the urine.
Creatinine is a waste product from muscle tissue breakdown. Kidneys usually remove creatinine from the body at a consistent rate, and it is found in urine. The test uses creatinine levels to normalize the albumin measurement, accounting for variations in urine concentration. This provides a more accurate assessment of albumin excretion. The first morning void is often collected for optimal accuracy.
Understanding the Normal Range
For healthy kidney function, the amount of albumin in the urine should be very low. A normal microalbumin creatinine ratio is less than 30 milligrams of albumin per gram of creatinine (mg/g) for a spot urine sample. This can also be expressed as less than 3 milligrams of albumin per millimole of creatinine (mg/mmol).
These numbers indicate that the kidneys are effectively filtering the blood and retaining albumin, which is their normal function. A result within this range suggests healthy kidney activity.
What Abnormal Results Indicate
When the microalbumin creatinine ratio exceeds the normal range, it indicates microalbuminuria: small but abnormal amounts of albumin leaking into the urine. This can be an early sign of kidney damage, even before other kidney function tests show abnormalities. An MACR between 30 and 300 mg/g (or 3 to 30 mg/mmol) is classified as moderately increased albuminuria.
Elevated MACR levels are associated with certain underlying health conditions. Diabetes is a common cause, as high blood sugar can damage kidney blood vessels, leading to albumin leakage. High blood pressure is another factor, as sustained pressure can harm kidney filters. Other conditions like heart disease or inflammatory conditions can also lead to elevated MACR. Sustained high levels warrant further investigation by a healthcare professional.
Factors Affecting Results and What Comes Next
Several factors can temporarily influence MACR results, leading to a transient elevation that does not reflect permanent kidney damage. Strenuous exercise within 24 hours, fever, urinary tract infection, certain medications, dehydration, or menstruation can temporarily increase albumin levels.
Because of these transient influences, a single abnormal MACR result does not automatically confirm kidney disease. Healthcare providers often recommend repeating the test, sometimes two or three times over three to six months, to confirm sustained elevated levels. Discuss all test results with a healthcare provider. They can interpret the findings in context of your health history and guide next steps, including follow-up tests or adjustments to lifestyle and treatment plans.