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Real members of MyLupusTeam have posted questions and answers that support our community guidelines, and should not be taken as medical advice. Looking for the latest medically reviewed content by doctors and experts? Visit our resource section.

I learned something new. The is a GFR through blood test and GFR through a urine test. What's the difference and which is more accurate.

A MyLupusTeam Member asked a question 💭
Martin, TN

My primary doctor told me my last test for my kidneys showed GFR through the bloodwork was 36, but the GFR through the urine test was 22, That was over a month ago. I am still waiting to see the kidney specialist. I was suppose to see them on June 1, but they couldn't find my recent test that they ordered. It didn't show that it was done. My kidneys hurt and this is driving me CRAZY

June 10
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A MyLupusTeam Member

The urine test requires collecting your urine for a whole 24 hours, and it tends to be more accurate than the blood test. However, it's cumbersome to do.

I suggest you make sure you're on a cancellation list for the nephrologist, Lisa. It also helps to check back once or twice a week, as you may be able to nab an appointment if there's a last-minute cancellation. Take care, and keep us posted.😘

June 11
A MyLupusTeam Member

@A MyLupusTeam Member GFR (glomerular filtration rate) is a kidney function test. See the first answer from AI for further details.

June 13
MyLupusTeam

That waiting game is absolutely maddening, especially when your kidneys are hurting. Let's break down the difference between the two GFR tests.

eGFR (Estimated GFR — Blood Test)
This is calculated using a blood test that measures creatinine (a waste product your muscles produce). It's an *estimate* based on your creatinine Show Full Answer

That waiting game is absolutely maddening, especially when your kidneys are hurting. Let's break down the difference between the two GFR tests.

eGFR (Estimated GFR — Blood Test)
This is calculated using a blood test that measures creatinine (a waste product your muscles produce). It's an *estimate* based on your creatinine level, age, and other factors. It's quick and commonly used, but it is an approximation.

mGFR or urine-based GFR (Urine Test)
This measures how well your kidneys are actually filtering waste by collecting urine, sometimes over 24 hours. It tends to be considered more directly measured and can be more precise.

The urine-based GFR of 22 is concerning and lower than the blood-based 36. Both numbers suggest your kidneys need close attention, particularly with lupus nephritis being a real risk with lupus. Given that your kidneys are hurting and it's been over a month, please don't wait passively. Here's what to consider doing right away:

- Call the nephrologist's office again and explain that your kidneys are actively hurting — this may escalate your appointment priority
- Ask your primary doctor to resend or reorder the missing test results directly to the specialist
- Request an urgent referral if pain is worsening — kidney pain with these GFR numbers warrants prompt attention
- Go to urgent care or the ER if the pain becomes severe

You absolutely deserve to be seen sooner. Advocate loudly for yourself here — this is urgent.

June 10
A MyLupusTeam Member

I don't even know what GFR is....sorry

June 11

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