This is the test that finds kidney disease before anything else does.
Albumin appears in the urine years before creatinine rises and long before you feel anything. A creatinine alone will not detect it. The ratio will.
Why a ratio
Urine concentration varies through the day. A dilute sample understates the albumin; a concentrated one overstates it. Dividing albumin by creatinine cancels that out, because creatinine excretion is relatively constant.
So a single random sample — no timed collection, no jug — gives a reliable number. That reliability is why this test replaced the 24-hour urine for screening.
What the number means
- Under 30 mg/g — normal (A1)
- 30 to 300 mg/g — moderately increased (A2). This is early kidney damage. It is silent, and it is where treatment does the most good.
- Above 300 mg/g — severely increased (A3)
- Above 3,500 mg/g — nephrotic range, usually with swelling and low blood albumin
The old terms "microalbuminuria" and "macroalbuminuria" have been retired. They implied a small problem and a large one; what the numbers actually describe is a continuous risk gradient with no safe threshold.
| Result (mg/g) | What it means |
|---|---|
| Under 30 | Normal |
| 30–300 | Moderately increased — the earliest treatable sign of kidney damage |
| Over 300 | Severely increased — act to protect kidney function |
Not just a marker
Albuminuria independently predicts progression to kidney failure and cardiovascular death — at every level of eGFR. Two patients with identical kidney function and different albumin levels face different futures.
And it is modifiable. ACE inhibitors, ARBs, SGLT2 inhibitors, and finerenone all reduce it, and the reduction itself improves outcomes. We treat the number, not only what it represents.
Confirming before acting
Fever, vigorous exercise, prolonged standing, heart failure, urinary infection, and menstruation can all raise albumin transiently.
A single abnormal result means repeat it. Two of three abnormal samples over three months establishes persistent albuminuria. Diagnosing chronic kidney disease off one dipstick after a hard workout is a mistake worth avoiding.
Who should be tested
Everyone with diabetes, annually. Everyone with hypertension. Anyone with a family history of kidney disease, reduced eGFR, cardiovascular disease, or obesity.
Annual albumin screening in diabetes is standard of care and is skipped constantly. It is among the highest-yield tests in medicine and among the least ordered.
The dipstick is not this test
A urine dipstick detects total protein, and it is insensitive to the low albumin concentrations that matter most. A negative dipstick does not rule out A2 albuminuria.
If someone tells you your urine protein was negative, ask whether an albumin-to-creatinine ratio was actually run.