To confirm a diagnosis of nephrotic syndrome, healthcare professionals use a specific set of blood and urine investigations. These tests are designed to identify the ‘triad’ of clinical features that define the condition: heavy protein loss in the urine, low protein levels in the blood, and high cholesterol. In the UK, these tests are standard across the NHS and are used to both diagnose the condition and monitor how well a patient is responding to treatment.
When you present with symptoms like swelling or frothy urine, your GP or specialist will first look for evidence that your kidney filters are ‘leaky’. Because nephrotic syndrome can lead to complications like blood clots or infections, these tests also help doctors assess your overall risk and determine the underlying cause. Understanding what each test measures can help you track your progress and understand the clinical decisions made by your renal team.
What We’ll Discuss in This Article
- The role of the urine dipstick in initial screening.
- How the Albumin-to-Creatinine Ratio (ACR) quantifies protein loss.
- Why serum albumin levels are critical for diagnosis.
- Using eGFR and Creatinine to measure overall kidney function.
- The importance of cholesterol and lipid profile testing.
- When additional blood tests are needed to find secondary causes.
Essential Urine Tests
The first step in diagnosing nephrotic syndrome is confirming that a significant amount of protein is escaping into the urine.
1. Urine Dipstick Test
This is the quickest screening tool, often performed in a GP surgery. A chemically treated strip is dipped into a fresh urine sample. If it turns a specific shade of green or blue, it indicates the presence of protein. In nephrotic syndrome, the result is usually ‘3+’ or ‘4+’, signifying a heavy leak.
2. Urine Albumin-to-Creatinine Ratio (ACR)
While a dipstick is a good start, the ACR is the ‘gold standard’ for accuracy in the UK. This laboratory test compares the amount of albumin (protein) to the amount of creatinine (a waste product).
- Nephrotic range: An ACR of 220 mg/mmol or higher is generally considered to be in the nephrotic range.
- This test is preferred over the older ’24-hour urine collection’ because it is more convenient for patients and highly reliable.
Source: https://www.kidney.org/kidney-failure-risk-factor-urine-albumin-creatinine-ratio-uacr
Essential Blood Tests
Once a protein leak is confirmed, blood tests are required to see how the body is reacting to that loss and to check the kidney’s efficiency.
1. Serum Albumin
This test measures the amount of albumin currently in your blood. In nephrotic syndrome, because so much is being lost in the urine, the blood levels drop significantly. A level below 30 g/L (hypoalbuminaemia) is a core requirement for diagnosis.
2. Kidney Function (Creatinine and eGFR)
Doctors measure ‘Creatinine’ (a waste product) to calculate your ‘Estimated Glomerular Filtration Rate’ (eGFR). This tells the specialist how well your kidneys are cleaning your blood. In early or ‘minimal change’ nephrotic syndrome, the eGFR may be normal, but in more severe cases, it may begin to fall.
3. Lipid Profile (Cholesterol)
Patients with nephrotic syndrome often have very high cholesterol and triglycerides. This happens because the liver goes into ‘overdrive’ trying to replace the lost blood proteins, and in the process, it produces excess fats.
| Test Name | Typical Nephrotic Result | What it Means |
| Urine ACR | >220 mg/mmol | Massive protein leakage into urine |
| Serum Albumin | <30 g/L | Dangerously low protein in the blood |
| Cholesterol | High | Liver overproduction of fats |
| eGFR | Variable | Overall ‘cleansing’ power of the kidney |
Screening for Secondary Causes
If the diagnosis is confirmed, the specialist will often order a ‘screen’ of other blood tests to see if a wider disease is causing the kidney damage.
- HbA1c: To check for underlying diabetes.
- Autoantibody Screen (ANA/dsDNA): To check for Lupus (SLE).
- Virology: To rule out Hepatitis B, Hepatitis C, and HIV, all of which can damage kidney filters.
- Complement Levels (C3/C4): Low levels can suggest certain types of autoimmune kidney inflammation.
Nephrotic vs. Nephritic Test Results
It is important to distinguish between these two syndromes, as the test results often point in different directions.
| Test Feature | Nephrotic Profile | Nephritic Profile |
| Urine Protein | Very High (>3.5g/day) | Mild to Moderate |
| Urine Blood | Usually None | High (Haematuria) |
| Serum Albumin | Very Low | Usually Normal |
| Blood Pressure | Often Normal | High |
To Summarise
To confirm nephrotic syndrome, UK doctors rely on a combination of high urine protein (ACR >220 mg/mmol) and low blood protein (Serum Albumin <30 g/L). Blood tests for cholesterol and kidney function (eGFR) provide a complete picture of the condition’s impact on the body. These tests are essential not only for the initial diagnosis but also for monitoring how effectively medications like steroids are stopping the protein leak.
If you experience severe, sudden, or worsening symptoms, such as difficulty breathing or extreme facial swelling, call 999 immediately.
Can a single urine test confirm the diagnosis?
No, a urine test confirms the protein leak, but blood tests for albumin levels are required to formally diagnose nephrotic syndrome.
Why is my cholesterol high if I eat healthily?
In nephrotic syndrome, high cholesterol is caused by the liver’s reaction to low blood protein, not by your diet.
How often will I need these tests?
During a flare-up, you may need tests weekly. Once in remission, they may be reduced to every few months or once a year.
Is eGFR the same as kidney function?
Yes, eGFR is the standard way UK doctors estimate how well your kidneys are filtering waste from your blood.
Does a normal creatinine level mean I’m fine?
Not necessarily. You can have a normal creatinine level but still have a massive protein leak that needs urgent treatment.
Do I need to fast before these blood tests?
Usually, you do not need to fast for kidney function tests, but you may be asked to fast for a more accurate cholesterol (lipid) profile.
Authority Snapshot
This article was reviewed by Dr. Stefan Petrov, a UK-trained physician with experience in general medicine and renal diagnostics. The information provided is in line with NHS and NICE clinical guidance regarding the investigation of proteinuria and glomerular disease. Our goal is to provide a clear explanation of the laboratory markers used to identify and monitor kidney health within the British healthcare system.
