Albuminuria is the appearance of the protein albumin in the urine. Normally the kidney filter lets almost none through, so even small amounts are an early signal of kidney damage.
It is one of the most sensitive early markers: albuminuria detects kidney disease long before creatinine rises. What is more, it independently predicts cardiovascular risk too.
Reference ranges
Assessed by the urine albumin-to-creatinine ratio (ACR/UACR, mg/g):
| Normal (A1) | < 30 mg/g |
| Microalbuminuria (A2) | 30 – 300 mg/g |
| Macroalbuminuria (A3) | > 300 mg/g |
| In 24-hour urine | normal < 30 mg/day |
What an elevated level means
Increased albuminuria means the kidney filter has begun to let protein through — an early sign of kidney damage.
Common causes: diabetic nephropathy and arterial hypertension (the two main ones), as well as glomerulonephritis and other kidney diseases. Importantly: even microalbuminuria is an independent cardiovascular risk factor, reflecting damage to the vessels in general.
What a low level means
Normal (low) albuminuria is a good sign: the kidney filter is working and not letting protein through.
In people with diabetes and hypertension, regular checking of albuminuria makes it possible to catch kidney damage at the earliest, still-reversible stage and to tighten control of blood pressure and blood sugar in time.
How the test is done
The most convenient is to test the albumin-to-creatinine ratio in a single (ideally morning) urine sample — this does not require a 24-hour collection. A 24-hour urine test is used less often.
The result is interpreted together with GFR: the combination of a reduced GFR and albuminuria defines the stage and risk of chronic kidney disease.
What affects the value
- Diabetes and hypertension — the main causes of albuminuria.
- Fever, a urinary infection, exertion — raise it temporarily.
- Dehydration — affects the result.
- Control of blood pressure and blood sugar — lowers albuminuria.
- Some drugs (ACE inhibitors, ARBs) — lower it.
- Pregnancy — requires separate assessment.
Assess kidney function
Albuminuria is assessed together with GFR — calculate your kidney filtration:
Frequently asked questions
What is microalbuminuria?
It is a small amount of albumin in the urine (an albumin-to-creatinine ratio of 30–300 mg/g) that is not yet visible on an ordinary protein test. It is the earliest sign of kidney damage, especially in diabetes and hypertension, and detecting it makes it possible to start protecting the kidneys in time.
Why is albuminuria linked to the heart?
The appearance of albumin in the urine reflects damage to the small vessels not only in the kidneys but throughout the body. So even a small amount of albuminuria independently raises the risk of heart attack and stroke, not just of kidney disease.
Does the test need to be repeated?
Yes. A single result can be a false positive because of fever, a urinary infection, physical exertion or dehydration. A diagnosis of persistent albuminuria is made on repeat confirmation — usually 2 positive tests out of 3 over 3–6 months.
Related terms
Sources
- Microalbuminuria — StatPearls (NCBI)
- MedlinePlus (NIH) — Microalbuminuria Test
- Microalbuminuria and cardiorenal risk (review). NCBI/PMC