Quick answer
What does a UACR result mean?
The urine albumin-to-creatinine ratio (UACR) compares albumin with creatinine in one urine sample, reducing the effect of how dilute or concentrated the urine is. A result below 30 mg/g (below 3 mg/mmol) is KDIGO category A1; 30 to 300 mg/g (3 to 30 mg/mmol) is A2; and above 300 mg/g (above 30 mg/mmol) is A3. Risk rises continuously rather than beginning at a magic cut-off. One elevated sample does not by itself diagnose chronic kidney disease: repeat confirmation, duration, eGFR and clinical context matter.See reference 1,See reference 2,See reference 3
The essentials in seven points
- UACR is the preferred spot-urine measure for detecting and monitoring albumin loss because it accounts for urine concentration.See reference 1,See reference 2
- A first-morning sample is preferred when practical; a random spot sample is acceptable when it is not available.See reference 1,See reference 2
- Albuminuria is a continuous kidney and cardiovascular risk marker; the A1, A2 and A3 categories organize risk rather than create absolute boundaries.See reference 1,See reference 2
- Exercise, infection, fever, menstruation, marked hyperglycaemia and other temporary factors can raise urine albumin.See reference 1
- An unexpected elevated result should usually be repeated and interpreted over time.See reference 1,See reference 3
- UACR and estimated GFR measure different aspects of kidney health and are stronger together.See reference 1
- The terms microalbuminuria and macroalbuminuria are older labels; current guidance favors moderately and severely increased albuminuria.See reference 1,See reference 2
What UACR measures
Albumin is a blood protein that healthy kidney filters largely retain. Creatinine is a waste product excreted in urine. Dividing urine albumin by urine creatinine helps normalize for how concentrated the sample is, so a spot sample can approximate daily albumin excretion without a routine 24-hour collection.See reference 1,See reference 2,See reference 3
UACR is not the same as serum albumin, urine total protein, a dipstick result or eGFR. Each answers a different question. A dipstick may miss lower levels of albumin, while eGFR estimates filtration from a blood marker.See reference 1,See reference 2,See reference 3
KDIGO albuminuria categories
- Category
- A1
- UACR in mg/g
- Below 30
- UACR in mg/mmol
- Below 3
- Plain-English interpretation
- Normal to mildly increased; risk still depends on eGFR and the wider clinical picture.See reference 1
- Category
- A2
- UACR in mg/g
- 30 to 300
- UACR in mg/mmol
- 3 to 30
- Plain-English interpretation
- Moderately increased; confirm persistence and assess kidney and cardiovascular risk.See reference 1,See reference 2
- Category
- A3
- UACR in mg/g
- Above 300
- UACR in mg/mmol
- Above 30
- Plain-English interpretation
- Severely increased; warrants timely clinical assessment and confirmation.See reference 1,See reference 2
Getting a result that can be interpreted
- Issue
- Sample timing
- Best practice
- Use a first-morning void when practical; a random spot urine is acceptable
- Why it matters
- First-morning sampling reduces some within-day variation.See reference 1,See reference 2
- Issue
- Collection
- Best practice
- Follow clean-catch and laboratory instructions
- Why it matters
- Contamination with blood or infection can complicate interpretation.See reference 1
- Issue
- Unexpected elevation
- Best practice
- Repeat under stable conditions when clinically appropriate
- Why it matters
- Chronic kidney disease requires persistence or other evidence, not one isolated number.See reference 1,See reference 3
- Issue
- Monitoring
- Best practice
- Prefer the same unit and laboratory, and compare alongside eGFR
- Why it matters
- Biological and analytical variation makes a single small change unreliable.See reference 1
Why UACR may be temporarily higher
- Context
- Hard exercise shortly before collection
- Possible effect
- Can transiently increase urine albumin
- Practical response
- Tell the clinician and consider repeat testing after usual activity resumes.See reference 1
- Context
- Fever, infection or acute illness
- Possible effect
- Can raise albumin excretion temporarily
- Practical response
- Treat the illness and confirm later if advised.See reference 1
- Context
- Markedly high glucose or blood pressure
- Possible effect
- May increase albumin leakage
- Practical response
- Interpret with current glucose, blood pressure and treatment context.See reference 1
- Context
- Menstruation or urinary bleeding
- Possible effect
- Blood contamination can distort the result
- Practical response
- Record the timing and ask whether recollection is preferable.See reference 1
What a persistent high UACR can mean
Persistent albuminuria can indicate damage to the kidney's filtering barrier and is used to classify chronic kidney disease. It is also associated with higher cardiovascular and kidney-progression risk. The number is a risk marker, not a diagnosis of one specific disease.See reference 1,See reference 2,See reference 3
Diabetes and high blood pressure are common contexts, but glomerular diseases, heart failure and other conditions can also raise UACR. Clinicians combine the result with eGFR, blood pressure, urine sediment, medicines, symptoms and the time pattern.See reference 1,See reference 3
What usually happens next
- Situation
- First A2 result
- Typical next question
- Was the sample collected during illness, heavy exercise, menstruation or marked hyperglycaemia, and when should it be repeated?
- Why
- Confirms whether albuminuria persists.See reference 1,See reference 3
- Situation
- A3 result
- Typical next question
- Does this need prompt repeat testing, kidney function review or specialist assessment?
- Why
- Higher albuminuria carries greater risk and may change management.See reference 1,See reference 2
- Situation
- Rising trend
- Typical next question
- Are blood pressure, glucose, medicines, eGFR and the urine sediment changing too?
- Why
- A trend is interpreted as a whole, not as a standalone percentage.See reference 1,See reference 2
- Situation
- A1 result with kidney risk factors
- Typical next question
- How often should screening be repeated?
- Why
- A1 today does not permanently exclude future kidney disease.See reference 1,See reference 3
When to seek timely care
Contact a clinician promptly for a very high or rapidly rising UACR, especially with swelling, reduced urine, visible blood, breathlessness, severe high blood pressure, pregnancy, or a major fall in eGFR. Seek urgent care for severe breathlessness, chest pain, confusion, fainting or rapidly worsening swelling. Do not wait for a repeat urine test when the person is acutely unwell.See reference 1,See reference 3
Frequently asked questions
Is UACR above 30 mg/g kidney disease?
It is above the A1 category and may be a sign of kidney damage, but one result does not establish chronicity. Repeat confirmation and the wider kidney assessment matter.See reference 1,See reference 2,See reference 3
Is a lower UACR always better?
Lower albumin excretion is generally favorable, but small changes can reflect normal variation. Judge meaningful trends with the same units, stable collection conditions and eGFR.See reference 1,See reference 2
Do I need a 24-hour urine collection?
Usually not for routine screening or monitoring. A spot UACR is recommended; a specialist may request timed collection for selected questions.See reference 1,See reference 2
What is the difference between UACR and eGFR?
UACR measures albumin leakage in urine; eGFR estimates filtering capacity from blood markers. Either can be abnormal while the other is not, so they are interpreted together.See reference 1
Are mg/g and mg/mmol the same?
They express the same ratio using different unit systems but have different numbers. Use the unit on the report and do not compare values without conversion.See reference 1
Is microalbumin a different protein?
No. It is an older term for a moderately increased amount of ordinary albumin. Current guidance favors the A2 category or 'moderately increased albuminuria.'See reference 1,See reference 2
References
- 1. KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease
Kidney Disease: Improving Global OutcomesGuideline
- 2. Assess Urine Albumin
National Institute of Diabetes and Digestive and Kidney DiseasesOfficial guidance
- 3. Albuminuria: Albumin in the Urine
National Institute of Diabetes and Digestive and Kidney DiseasesOfficial guidance
Editorial transparency
- Published by
- LongevityMate Editorial Team
- Published
- Updated
Medical disclaimer
Educational information, not diagnosis or a personal kidney treatment plan. Interpret UACR with the exact unit, sample conditions, repeat results, eGFR, blood pressure, glucose, pregnancy status, medicines, symptoms and clinical history. Do not start, stop or change kidney, blood-pressure or diabetes medicines from one urine result.