Kidney Function Tests Explained: Creatinine, eGFR, Urea and Urine Albumin (UACR)

Quick answer: The two core kidney tests are a blood test for creatinine, converted into an eGFR (how well the kidneys filter), and a urine albumin-to-creatinine ratio, or UACR (whether the kidneys are leaking protein). Doctors usually use them together, because early kidney disease can show up in one before the other. Neither needs fasting. At St. Luke's in Ja-Ela, Serum Creatinine with GFR costs LKR 700 and Urine Microalbumin / UACR costs LKR 1,400. A single abnormal result does not confirm kidney disease — it is normally repeated and read by your doctor alongside your health history.

Kidney disease is often called "silent" because the kidneys can lose a good deal of function before a person feels anything. That is why doctors check the kidneys with blood and urine tests in people with diabetes, high blood pressure and other risk factors — rather than waiting for symptoms. This guide explains the tests you are most likely to see on a request form.

The main kidney tests at a glance

Creatinine and eGFR: how well are the kidneys filtering?

Creatinine is a waste product from normal muscle activity. Healthy kidneys filter it out of the blood at a fairly steady rate, so when filtering slows, creatinine tends to rise.

On its own, though, creatinine is an imperfect measure, because it depends on how much muscle you have, your age, diet and hydration. That is why labs convert it into an estimated glomerular filtration rate (eGFR) using an equation that includes factors such as age and sex. MedlinePlus notes that eGFR is generally considered more accurate than creatinine alone, but also that creatinine can stay normal in early kidney disease and that a high creatinine does not always mean kidney disease (MedlinePlus: Creatinine Test).

Things that can temporarily push creatinine up include dehydration, intense exercise and a large meat meal. Some medicines and supplements can also affect it, so tell your doctor everything you take.

UACR: are the kidneys leaking protein?

Healthy kidneys keep almost all protein in the blood. One of the earliest signs of kidney damage — especially in diabetes and high blood pressure — is a small amount of a protein called albumin appearing in the urine.

The urine albumin-to-creatinine ratio (UACR) measures this precisely from a single urine sample. The UK's National Institute for Health and Care Excellence (NICE) recommends using ACR rather than a dipstick to detect protein in the urine, because it is more sensitive at low levels (NICE guideline NG203). The "albumin" line on a routine Urine Full Report is useful as a broad screen, but it is not a substitute for a UACR when kidney damage is the question.

Because exercise, fever, infection and periods can raise urine albumin temporarily, doctors usually confirm a raised UACR with a repeat sample before drawing conclusions.

Who is usually tested?

NICE recommends offering kidney testing with eGFR and ACR to adults with risk factors including (NICE NG203):

• Diabetes
• High blood pressure
• Previous acute kidney injury
• Cardiovascular disease
• Gout
• A family history of kidney failure or inherited kidney disease
• Blood or protein found in the urine by chance
• Some conditions that affect several organs, such as lupus

Doctors also monitor kidney function in people taking certain long-term medicines that can affect the kidneys. NICE specifically notes that age, sex, ethnicity or weight alone are not reasons to test without other risk factors.

A note on kidney disease in Sri Lanka

You may have heard about chronic kidney disease of uncertain cause (CKDu) in Sri Lanka. Research on CKDu has focused mainly on dry-zone farming regions such as the North Central and Uva provinces, and screening studies there also rely on eGFR and urine albumin (BMC Nephrology, 2019). For most people around Ja-Ela, the reasons a doctor checks the kidneys are more often diabetes, high blood pressure and the other risk factors listed above.

How to prepare

• No fasting is needed for creatinine, eGFR, urea, electrolytes or UACR. If your form also includes a fasting test, fast for that one.
• Avoid a very large meat meal and heavy exercise the evening before a creatinine test.
• Drink normally — neither dehydrated nor over-hydrated.
• For UACR, a first-morning urine sample is often preferred — follow your doctor's instructions.
• Keep taking your medicines unless the doctor who requested the test tells you otherwise.

Reading the result — what a number can and cannot tell you

Kidney disease is generally not diagnosed from a single test. Guidelines describe chronic kidney disease in terms of abnormal results that persist for more than three months, and they grade it using both eGFR and ACR together (NICE NG203). That is why your doctor may:

• repeat a test before making any decision,
• look at the trend over several results (ideally from the same laboratory), and
• consider your blood pressure, blood sugar, medicines and other findings.

We deliberately do not list cut-off numbers here. Reference ranges vary with the method and with age and sex, and your report shows the range used for your sample. Please discuss your results with your doctor rather than drawing conclusions from the number alone.

Kidney tests at St. Luke's, Ja-Ela

We run blood chemistry on our BioSystems A15 biochemistry analyser and electrolytes on a dedicated Audicom electrolyte analyser — see our lab technology.

If your doctor has asked for several kidney tests, two of our health packages group them:

• Kidney Health Profile — LKR 3,500: Serum Electrolytes, Ionized Calcium, Serum Creatinine with GFR, Serum Uric Acid and Urine Full Report.
• Diabetic Kidney Profile — LKR 3,600: Urine Microalbumin (UACR), Serum Electrolytes, Ionized Calcium and Serum Creatinine with GFR.

Walk in to our lab at No. 67, Old Negombo Road, Ja-Ela (Mon–Sat 07:00–19:30, Sun 07:30–12:30), or book home collection — useful for regular monitoring in Ragama, Wattala, Kandana and the surrounding towns. Call 071 123 1954 and read out your request form; we will confirm the tests and price before you come.

Frequently asked questions

What is the difference between creatinine and eGFR?

Creatinine is the measured level of a waste product in your blood. eGFR is a calculated estimate of how well your kidneys filter, worked out from creatinine and factors such as age and sex. eGFR is generally more informative than creatinine alone.

Do I need to fast for a kidney function test?

No. Creatinine, eGFR, urea, electrolytes and UACR do not need fasting. Avoid a very large meat meal and heavy exercise the evening before.

Is UACR the same as the albumin on my urine report?

No. The albumin line on a Urine Full Report is a rough screen. UACR is a more sensitive measurement designed to pick up small amounts of albumin, which matters most for people with diabetes or high blood pressure.

My creatinine is slightly high. Do I have kidney disease?

Not necessarily. Dehydration, exercise, a high-meat meal, muscle mass and some medicines can raise creatinine. Your doctor will usually repeat the test and look at eGFR, urine albumin and your overall health before reaching any conclusion.

How often should kidney function be checked?

That depends on your health and is decided by your doctor. People with diabetes or high blood pressure are commonly checked at least once a year.

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Sources

• MedlinePlus. Creatinine Test.
• National Institute for Health and Care Excellence. Chronic kidney disease: assessment and management (NG203).
• BMC Nephrology, 2019. Article 10.1186/s12882-019-1477-9 — eGFR and CKDu screening in Sri Lanka (reviewer to confirm full citation).
• MedlinePlus. How to Understand Your Lab Results.

This article is general health information, not medical advice. Do not start, stop or change any medicine based on a test result without speaking to your doctor. If you notice swelling, passing much less urine than usual, or feel very unwell, seek medical care promptly.