Kidney function tests use blood and urine samples to check how well your kidneys are working. Blood creatinine helps estimate how much blood the kidneys filter. A urine albumin-to-creatinine ratio, or ACR, checks for protein leakage that can be a sign of kidney damage.
If you are arranging these tests in Pakistan, take the doctor's prescription with you. The lab needs the names of the tests requested, particularly when the slip includes a urine test as well as a blood test.
KFT and RFT on a Pakistani test slip
KFT means kidney function test; RFT means renal function test. You may also see 'renal profile'. These names describe kidney testing, but the panel name alone does not tell you whether urine ACR is included.
Before paying for a panel, show the lab your prescription and confirm the tests it will carry out. Ask whether eGFR will appear with the creatinine result, and whether a separately requested urine ACR is included in the quotation. Check when both reports will be ready, especially if you have a follow-up appointment booked.
For home sample collection, confirm that the service can collect every sample on the prescription and provide the correct urine container. Keep a copy of the request alongside the results.
Why your doctor may request these tests
Diabetes and high blood pressure increase the risk of kidney disease. Heart disease and a family history of kidney failure are also reasons to discuss testing with your doctor. Early chronic kidney disease can have no symptoms, so feeling well does not tell you whether a check is due.
Testing may also be needed after an earlier abnormal result, while monitoring an existing kidney condition, or when you take a medicine that can affect the kidneys. Your doctor can set the testing schedule for your circumstances.
Swelling, blood or foam in the urine, and a change in how often you pass urine are symptoms to discuss at an appointment. The doctor will consider them alongside your history and test results.
Creatinine: read the value with its reference range
Creatinine is a waste product made by your muscles. Your kidneys normally remove it from the blood through urine. When filtration falls, blood creatinine can rise.
Use the reference range and units printed beside your result. A single 'normal creatinine' number is not suitable for everyone: muscle mass, age, food and physical activity affect the amount your body makes.
A high result needs an explanation. Dehydration, intense exercise and a diet high in meat can also raise creatinine. A result within the reference range can occur in early kidney disease, which is why the doctor may look at eGFR and urine findings too.
eGFR: what a lower number means
Estimated glomerular filtration rate, shortened to eGFR, is a calculation of how well the kidneys filter blood. It usually uses blood creatinine together with details such as your age and sex. The result is commonly written in mL/min/1.73 m², a unit adjusted to a standard body surface area.
An eGFR below 60 needs medical assessment. To diagnose chronic kidney disease, doctors generally look for reduced filtration or evidence of kidney damage lasting more than three months. A new low result still needs to be assessed when it is found; ask your doctor when it should be repeated.
An eGFR of 60 or above does not exclude kidney disease when there are other signs of damage, such as raised urine albumin. Take earlier reports to the appointment so the doctor can see whether the result is stable or has changed.
Urine ACR: checking for albumin
Albumin is a protein in the blood. Larger amounts passing into the urine can indicate kidney damage. ACR compares urine albumin with urine creatinine to measure that leakage more accurately.
A spot urine sample is used for ACR screening. The request may call it urine ACR, UACR or microalbumin-to-creatinine ratio. Confirm that the lab is carrying out the requested ratio test if your prescription also mentions a routine urine examination.
Urine albumin above 30 mg/g creatinine can be a marker of kidney damage. Check the units before comparing numbers: mg/g and mg/mmol use different scales. Show the complete report to your doctor, who can interpret it alongside eGFR and decide whether you need another sample.
Before the blood and urine samples
Ask the lab or prescribing doctor for preparation instructions before your visit. Fasting may be needed when creatinine is part of a wider set of blood tests. You may also be asked to avoid meat beforehand because it can temporarily raise creatinine.
Tell the doctor about your medicines and supplements, including anything bought without a prescription. Do not stop prescribed medicine to prepare for a test unless the prescriber tells you to.
Use the urine container supplied by the lab and follow its collection and delivery instructions. If the prescription asks for a 24-hour urine collection, get the separate instructions for collecting and storing every required sample.
If you plan to attend during Ramadan, ask about the appointment time and preparation requirements beforehand. Discuss any change to medicine timing with the prescribing doctor.
Taking the report back to your doctor
Take both blood and urine reports, any earlier kidney results, and your medicine list to the doctor who requested the tests. Ask which result needs follow-up, when to repeat it and whether you need to see a nephrologist, a doctor who treats kidney disease.
Further investigations depend on the findings. These may include other blood or urine tests and a kidney ultrasound. One high creatinine reading cannot establish the cause, so let the doctor review the results before buying another test package.
