Albumin and microalbumin are two terms often encountered in discussions about health, particularly concerning kidney function. While both relate to the protein albumin, their presence in different parts of the body, or in different amounts, carries distinct implications for your health.
What is Albumin?
Albumin is the most abundant protein found in human blood plasma, making up approximately 55% of the total protein content. It is primarily produced by the liver, with liver cells synthesizing about 10 to 15 grams daily. Once produced, albumin circulates throughout the bloodstream, performing important functions.
One of albumin’s main roles is maintaining osmotic pressure, which helps keep fluid within the blood vessels and prevents it from leaking into surrounding tissues. Additionally, albumin acts as a transport protein, binding to and carrying various substances such as hormones, vitamins, fatty acids, drugs, and calcium, facilitating their circulation. A standard albumin blood test measures the overall level of this protein in the blood, with normal adult levels ranging from 3.5 to 5.5 grams per deciliter (g/dL).
What is Microalbumin?
Microalbumin refers to the presence of small, detectable amounts of albumin in the urine. Healthy kidneys normally act as filters, preventing most albumin from passing from the blood into the urine.
The detection of microalbumin in urine, a condition known as microalbuminuria, signals that the kidneys are not functioning optimally. Even these small amounts can indicate early kidney damage. Microalbumin levels are measured through a urine test, using an albumin-to-creatinine ratio (ACR). A normal ACR is less than 30 milligrams of albumin per gram of creatinine (mg/g), while microalbuminuria is defined by an ACR between 30 and 300 mg/g.
Why the Difference Matters
The distinction between albumin in the blood and microalbumin in the urine is significant because it highlights different aspects of health. While adequate albumin levels in the blood are necessary for overall bodily function, the presence of even small amounts of albumin in the urine, microalbuminuria, is a sign of concern. This indicates that the kidney’s filtering units, the glomeruli, may be damaged and are allowing albumin to leak through.
Detecting microalbuminuria is important for individuals with conditions such as diabetes or high blood pressure, as these are major risk factors for kidney disease. Microalbuminuria can be an early indicator of kidney damage, often appearing before other symptoms or abnormalities in traditional kidney function tests. Early detection allows for timely interventions, such as aggressive blood pressure and blood glucose control, which can help slow or prevent the progression of kidney disease.
Elevated microalbumin levels also signal an increased risk of cardiovascular disease, including heart attack and stroke, even in individuals without a diabetes diagnosis. Regular monitoring of the urine albumin-to-creatinine ratio is recommended to assess treatment effectiveness and prevent further complications. Lifestyle modifications, including dietary changes and regular exercise, along with medications like ACE inhibitors or ARBs, are part of the management strategy to reduce microalbuminuria and protect both kidney and cardiovascular health.