cpt code for glomerular filtration rate​

If you have ever looked at a lab report for kidney function, you have probably seen the term glomerular filtration rate (GFR). It is one of the most important numbers for understanding how well the kidneys are working. But when it comes to billing and coding, many medical professionals and office staff ask the same question:

What is the correct CPT code for glomerular filtration rate?

The answer is not always as simple as picking a single five-digit number. That is because GFR can be measured in different ways. Sometimes it is estimated using a formula. Other times it is measured directly using a special substance like inulin or iohexol.

This guide walks you through everything you need to know. You will learn the most common CPT codes, when to use each one, and how to avoid costly mistakes. Let us start with the basics.

What Is Glomerular Filtration Rate (GFR)?

Before we talk about codes, it helps to understand what GFR actually measures.

Your kidneys have millions of tiny filters called glomeruli. Each day, they clean your blood by removing waste and extra fluid. The glomerular filtration rate tells you how many milliliters of blood your kidneys filter per minute.

A normal GFR is usually 90 or higher. A lower number may suggest kidney disease.

Doctors use GFR to:

• Diagnose chronic kidney disease (CKD)

• Monitor kidney function over time

• Adjust medication dosages

• Decide when to start dialysis or plan a kidney transplant

There are two main ways to get a GFR number:

1. eGFR (estimated GFR) – calculated using a blood test (creatinine or cystatin C) plus age, sex, and race.

2. mGFR (measured GFR) – a direct test using an injected substance like iohexol or iothalamate.

The CPT code you choose depends entirely on which method your lab or clinic uses.

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Why Knowing the Correct CPT Code Matters

Using the wrong CPT code for glomerular filtration rate can lead to:

• Claim denials

• Payment delays

• Compliance issues with Medicare and private insurers

• Unnecessary audits

Billing for GFR is not as common as billing for a basic metabolic panel. That means even experienced coders sometimes get confused. The good news is that once you understand the logic, the codes become easy to remember.

Important note: Always check your local payer policies. Medicare and private insurers may have different requirements for GFR testing, especially for mGFR.

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Main CPT Codes for Glomerular Filtration Rate

Below is a complete list of CPT codes that relate to GFR. Some are for estimated GFR, others for measured GFR, and a few are part of larger lab panels.

Estimated GFR (eGFR) Codes

Most clinics use eGFR because it is simple and low-cost. It usually comes from a basic or comprehensive metabolic panel.

In practice, 80047 (BMP with eGFR) and 80069 (CMP with eGFR) are the most common codes for estimated GFR. Many labs have switched to these codes automatically.

Measured GFR (mGFR) Codes

Direct measurement of GFR is less common. It is more expensive and time-consuming. However, it is more accurate in certain situations, such as:

• Very muscular or very thin patients

• Unusual diets (e.g., vegetarian, creatine supplements)

• Before kidney donation

Most modern measured GFR tests use iohexol (82370) or iothalamate (82530). The injection is usually billed separately under 82542 if not included in the lab code.

GFR from Urine Collection

Sometimes GFR is calculated using a 24-hour urine collection. This provides a creatinine clearance, which approximates GFR.

Note: Creatinine clearance (82575) is not the same as eGFR, but it is often used as a substitute when mGFR is not available. Many payers accept it for kidney function monitoring.

How to Choose the Right Code: A Simple Flowchart in Words

1. Did the lab run a blood test and report an eGFR number?
   → Use 80047 (BMP with eGFR) or 80069 (CMP with eGFR).

2. Did the lab run creatinine (82565) and add an eGFR calculation separately?
   → Use 82565 plus any additional calculation code if required by payer.

3. Did the doctor order a measured GFR using iohexol or iothalamate?
   → Use 82370 (iohexol) or 82530 (iothalamate), plus possibly 82542 for injection.

4. Did the patient do a 24-hour urine collection for creatinine clearance?
   → Use 81050 (collection) + 82570 (urine creatinine) + 82575 (clearance calculation).

5. Is the test being done to screen for kidney disease without symptoms?
   → Check medical necessity. Many payers limit GFR testing to patients with risk factors like diabetes or hypertension.

Real-World Examples

Let’s look at three typical patient cases. This will help you see how the codes work in practice.

Example 1: Routine Annual Physical

A 55-year-old woman with type 2 diabetes comes in for her yearly checkup. The doctor orders a comprehensive metabolic panel to check her blood sugar, electrolytes, and kidney function. The lab runs a CMP and automatically includes eGFR.

Correct CPT code: 80069

Example 2: Measured GFR for Kidney Donor

A healthy 32-year-old man is being evaluated as a living kidney donor. The nephrologist wants a precise GFR measurement. Iohexol is injected, and blood samples are drawn at specific times.

Correct CPT codes:

• 82542 (injection procedure)

• 82370 (iohexol measurement)

Some payers bundle these into one code. Verify with your lab.

Example 3: Follow-Up for Chronic Kidney Disease

A 70-year-old man with stage 3 CKD has a basic metabolic panel ordered every three months. The lab includes eGFR automatically.

Correct CPT code: 80047

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Billing Tips and Common Mistakes

Even good coders slip up sometimes. Here are the most frequent errors with GFR coding.

Mistake 1: Using 80048 Instead of 80047

80048 is the basic metabolic panel without eGFR. If your lab reports eGFR, do not use this code. Use 80047 instead. The difference is small but important. Medicare has been known to deny claims when the wrong BMP code is used.

Mistake 2: Billing 82565 and an eGFR Add-On Code Separately

Many labs automatically calculate eGFR when they run a creatinine (82565). You usually cannot bill extra for the calculation. It is considered part of the lab work.

Mistake 3: Using mGFR Codes for Routine Screening

Measured GFR is expensive. Insurers will deny it unless there is a strong medical reason. Always document why mGFR was necessary instead of eGFR.

Mistake 4: Forgetting the 24-Hour Urine Collection Code

If a patient brings in a 24-hour urine sample for creatinine clearance, you need both the collection code (81050) and the urine creatinine code (82570). Some offices forget the collection code, which covers patient instruction and handling.

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Medicare and GFR Coding

Medicare covers GFR testing under specific conditions. For eGFR, Medicare considers it part of the BMP or CMP. You do not need a separate diagnosis code for eGFR itself.

For measured GFR (iohexol or iothalamate), Medicare requires:

• A diagnosis of kidney disease where eGFR is unreliable, or

• Evaluation for kidney donation, or

• Chemotherapy dosing that depends on precise kidney function

Always check your local Medicare Administrative Contractor (MAC) guidelines. Some MACs have local coverage determinations (LCDs) for mGFR.

Quote from CMS: “Medicare covers eGFR as part of a basic or comprehensive metabolic panel when the patient has a condition that affects kidney function, such as diabetes or hypertension.”

Frequently Asked Questions (FAQ)

1. What is the single CPT code for glomerular filtration rate?

There is no single code. The most common codes are 80047 (BMP with eGFR) and 80069 (CMP with eGFR) for estimated GFR. For measured GFR, use 82370 (iohexol) or 82530 (iothalamate).

2. Is eGFR the same as creatinine clearance?

No. eGFR is calculated from blood creatinine, age, sex, and sometimes race. Creatinine clearance requires both a blood sample and a 24-hour urine collection. They are similar but not identical.

3. Can I bill for eGFR separately?

No. In most cases, eGFR is included in the metabolic panel code (80047 or 80069). You cannot add a separate code for the calculation.

4. Does insurance cover measured GFR?

Sometimes. Measured GFR (iohexol or iothalamate) is usually covered for specific medical reasons like kidney donation evaluation or when eGFR is known to be inaccurate. Pre-authorization may be required.

5. What diagnosis code should I use with GFR CPT codes?

Use the reason for the test. Common ICD-10 codes include:

• E11.22 – Type 2 diabetes with diabetic CKD

• N18.3 – Stage 3 CKD

• Z00.00 – Annual physical (only for screening if allowed)

• Z52.4 – Living kidney donor evaluation

6. How often can GFR be billed?

For routine monitoring of stable CKD, once every 3 to 6 months is typical. For acute kidney injury or medication adjustments, more frequent testing may be covered. Check your payer policy.

7. What is the difference between 80047 and 80048?

80047 includes eGFR. 80048 does not. If your lab reports eGFR, use 80047. If not, use 80048.

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Additional Resources

For the most current coding guidelines and payer policies, refer to these trusted sources:

• CMS Clinical Laboratory Fee Schedule – www.cms.gov

• American Medical Association CPT® Codebook – www.ama-assn.org

• National Kidney Foundation – GFR Guidelines – www.kidney.org

Link to additional resource:
Centers for Medicare & Medicaid Services – Lab Code List – This official PDF includes pricing and coverage indicators for all GFR-related codes.

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Final Practical Advice

Here is a quick checklist to keep near your coding desk:

• Is this eGFR or mGFR?

• If eGFR: use 80047 (BMP) or 80069 (CMP)

• If mGFR with iohexol: use 82370 (plus injection code if needed)

• If 24-hour urine: use 81050 + 82570 + 82575

• Check medical necessity documentation

• Verify local payer coverage for mGFR

• Do not bill eGFR separately from BMP/CMP

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Conclusion

In summary: The correct CPT code for glomerular filtration rate depends on the testing method. For routine estimated GFR, use 80047 or 80069. For measured GFR with iohexol or iothalamate, use 82370 or 82530. Always document medical necessity and check payer policies to avoid denials.