Urine albumin test: what the result means

According to MedlinePlus, with healthy kidneys there should be less than 30 mg of albumin per gram of creatinine — healthy kidney filters barely let it through into the urine. From 30 to 300 mg/g is considered microalbuminuria, an early and often reversible sign of kidney damage, while above 300 mg/g is macroalbuminuria, which is linked to more pronounced damage. The methods and ranges laboratories use can differ slightly, so it is worth checking your own result against the laboratory range printed on your report rather than against a general guide figure alone. The result is usually measured as an albumin-to-creatinine ratio in a single urine sample rather than as an albumin amount on its own, because this avoids the error caused by different dilution.

The albumin concentration in a single urine sample depends on how much fluid the person drank that day and how dilute the urine is as a result. The same state of the kidneys can give a different absolute figure if the sample is taken after drinking a lot of fluid or, conversely, during dehydration. Comparing the amount of albumin with the amount of creatinine in the same sample gives a ratio (mg of albumin per gram of creatinine) that no longer depends on dilution, because creatinine in the urine also changes in a similar direction. That is why this ratio, rather than a single albumin figure, is considered the more accurate and most commonly used measure.

Not necessarily. The most common cause is diabetes and the kidney damage associated with it, and other causes include arterial hypertension, immune or inflammatory kidney diseases and a narrowed kidney artery. But a rise can also be caused by temporary circumstances unrelated to chronic kidney disease — fever, intense physical exercise or dehydration shortly before the sample is taken. According to MedlinePlus, a single raised result is not in itself enough to draw any conclusion: it needs to be confirmed by a repeat test, whose timing is decided by the doctor, ideally once the temporary causes have been removed. Until that is done, a single raised result shows only that further investigation is needed, not what specific cause produced it.

MedlinePlus states that for people with type 1 or type 2 diabetes this test is recommended as an annual check. A high blood sugar level can damage the kidney filters (glomeruli) over time, and albumin in the urine often starts to rise before other, standard kidney function markers change, such as creatinine in the blood or the estimated glomerular filtration rate. Checking this marker every year therefore helps to spot beginning kidney damage while it is still at an early, often reversible stage, and to take measures in time to slow it down. Such an annual check is especially important for people who were diagnosed with diabetes long ago, because a longer-standing disease increases the likelihood of kidney damage.

According to MedlinePlus, no special preparation is usually needed — there is no need to fast or to change your usual routine. Even so, it is advisable to avoid intense physical exercise and eating a lot of meat before the test, as both of these can temporarily raise the result and distort the true picture. It is also worth mentioning to your doctor if you have recently had a fever, an infection or dehydration, because these states can affect the result in a similar way even if the kidneys are in fact undamaged. Such an explanation helps the doctor to assess the result more accurately and, if necessary, to decide on a repeat test at a later time.

According to MedlinePlus, the boundary between these two conditions is set by the albumin-to-creatinine ratio in the urine. From 30 to 300 mg of albumin per gram of creatinine marks microalbuminuria — the earlier stage, in which kidney damage is often still reversible if the causes behind it, such as diabetes or hypertension, are brought under control in time. 300 mg/g creatinine and above marks macroalbuminuria, which is linked to more pronounced, longer-standing and less easily reversible kidney damage. In both cases the exact result is assessed together with other kidney function markers, and the boundary between these two categories is not rigid, so each case is discussed with a doctor individually.