CPT code 83540: Iron (Fe) quantitative test, coverage and fees

Key Takeaways

CPT code 83540 (Iron; quantitative) measures total serum iron and falls under the Pathology and Laboratory / Chemistry Procedures section of the AMA CPT code set.

Medicare covers CPT 83540 under NCD 190.18 for iron deficiency anemia, hemochromatosis, hemolytic anemia, suspected iron poisoning, and monitoring of iron therapy.

The 2026 national average Medicare allowed amount is approximately $8.44, with variation by MAC jurisdiction. Routine screening without documented medical necessity is not covered.

Pabau’s claims management software links CPT codes to ICD-10 diagnoses and submits claims electronically, reducing manual coding steps for chemistry panel orders like 83540.

The official AMA descriptor for CPT code 83540 is “Iron; quantitative.” The code is maintained by the American Medical Association (AMA) and sits within the Pathology and Laboratory section of the CPT code set, specifically under the Chemistry Procedures subsection (codes 82009-84999).

The test itself measures the concentration of iron (Fe) in serum or plasma. Results are reported in micrograms per deciliter (mcg/dL) or micromoles per liter (umol/L), depending on the laboratory’s reporting convention. Unlike ferritin, which reflects stored iron, serum iron measured by CPT 83540 represents the iron bound to transferrin that is actively circulating in the bloodstream.

Clinical conditions CPT code 83540 supports

Clinicians order this test when they need a direct measure of circulating iron to differentiate iron deficiency from other anemias or to assess iron overload. Common clinical applications include:

• Iron deficiency anemia workup – serum iron is low; typically ordered alongside TIBC (CPT 83550) and ferritin (CPT 82728)
• Hemochromatosis monitoring – serum iron is elevated; helps track iron overload in hereditary and acquired forms
• Hemolytic anemia evaluation – distinguishes hemolysis-related iron release from dietary or absorption causes
• Iron poisoning assessment – acute ingestion causes rapid serum iron elevation before symptoms fully develop
• Iron supplementation therapy monitoring – confirms therapeutic response and prevents over-supplementation
• Anemia of chronic disease differentiation – serum iron is low but ferritin is normal or elevated, unlike true deficiency

In practice, CPT 83540 rarely travels alone. Most ordering providers request a full iron study panel that includes at least TIBC (CPT 83550) alongside total iron, because the transferrin saturation ratio (serum iron divided by TIBC, multiplied by 100) provides more diagnostic information than either value in isolation.

When to order CPT code 83540

Medicare and most commercial payers cover CPT code 83540 when there is a documented clinical indication tied to a supporting ICD-10 code. The ordering provider’s chart must record why the test was clinically necessary for that specific patient encounter.

The most common ordering scenarios are symptomatic anemia workup (fatigue, pallor, dyspnea on exertion), follow-up after a low hemoglobin or hematocrit result on a complete blood count, and monitoring of known hemochromatosis. Family history of hereditary hemochromatosis without symptoms does not automatically qualify for Medicare coverage under NCD 190.18 without additional clinical documentation of suspected disease.

Medicare coverage for serum iron studies (NCD 190.18)

The Centers for Medicare and Medicaid Services (CMS) governs Medicare coverage for serum iron testing under National Coverage Determination (NCD) 190.18. This NCD covers both CPT 83540 (serum iron) and CPT 83550 (TIBC) when the tests are medically necessary. Good insurance eligibility verification before ordering reduces the risk of after-the-fact denials for non-covered indications.

Covered indications under NCD 190.18

• Iron deficiency anemia
• Hemolytic anemia
• Hemochromatosis (hereditary or acquired)
• Suspected iron poisoning or toxicity
• Monitoring of iron therapy (supplemental or intravenous iron)

Non-covered indications under NCD 190.18

• Routine screening without a documented clinical indication
• Annual wellness visits where iron status is not specifically in question
• Testing that lacks a linked ICD-10 code supporting medical necessity

CMS requires that the ordering provider document the specific clinical indication in the patient record. Using a medical claims clearinghouse that validates ICD-10-to-CPT pairings before submission is one of the most effective ways to catch coverage mismatches before they become denials.

ICD-10 codes that support medical necessity

Every claim for CPT 83540 must carry at least one ICD-10-CM diagnosis code that establishes medical necessity. The CMS ICD-10 codes page is the authoritative source for current code validity. The table below lists the most commonly used supporting diagnoses for serum iron testing.

Use the most specific ICD-10 code available. Submitting D50.9 (unspecified iron deficiency anemia) when a more specific code applies (such as D50.0 for blood-loss anemia) can trigger additional review requests from some MACs. Verify current code validity against the applicable fiscal year’s ICD-10-CM release, as codes are updated annually each October.

2026 fee schedule and Medicare reimbursement

CPT 83540 is reimbursed under the Clinical Laboratory Fee Schedule (CLFS), not the Physician Fee Schedule (PFS). The CLFS is updated annually by CMS. According to publicly available fee schedule data cited by multiple coding reference sources, the 2026 national average Medicare allowed amount for CPT 83540 is approximately $8.44, though this figure should be verified against the current CMS CLFS release for your specific MAC jurisdiction before billing.

Rates vary by Medicare Administrative Contractor (MAC) jurisdiction. Practices in high-cost urban areas may receive slightly higher rates than the national average; rural and lower-cost regions sometimes fall below it. Use the CMS Physician Fee Schedule lookup and the annual CLFS data file to verify the exact rate for your jurisdiction. Receiving electronic remittance advice (ERA) after each claim batch makes it easier to spot rate discrepancies and catch underpayments before they accumulate.

Note: rates for 83550, 82728, and 85025 above are illustrative typical ranges from published sources and should be confirmed against the current CLFS before use in billing. Only the 83540 figure has been cited by multiple coding reference sources specifically for 2026.

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Pabau connects CPT code assignment, ICD-10 linking, and electronic claim submission in one workflow. See how practices using Pabau reduce iron panel billing errors and speed up reimbursement.

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Related CPT codes: Iron panel and anemia workup

CPT 83540 rarely bills in isolation. Understanding how it relates to companion codes prevents undercoding (missing billable tests) and overcoding (bundling errors). The AAPC CPT code lookup provides descriptor cross-references useful for confirming which codes can be billed together.

83540 vs 83550: What each code measures

CPT 83540 measures the actual iron concentration in serum. CPT 83550 measures the iron binding capacity of transferrin, specifically the total amount of iron that transferrin could carry if fully saturated. Together, they produce transferrin saturation: (83540 result / 83550 result) x 100. A saturation below 16% typically indicates iron deficiency. A saturation above 45-50% raises concern for iron overload or hemochromatosis.

Both codes are covered under NCD 190.18 when the clinical indication is documented. Billing one without the other is clinically unusual for a full iron deficiency workup, though 83540 alone can be appropriate for a quick monitoring check during iron supplementation therapy. Payers occasionally question a lone 83540 claim without an accompanying 83550 for an initial anemia evaluation, so document clearly when ordering only the serum iron test.

Documentation and billing requirements

Solid documentation protects against audits and is the primary defense against denied claims. Solid medical billing compliance practices for CPT 83540 center on five documentation elements. Practices that build these into their ordering workflow, rather than chasing documentation after a denial, submit cleaner claims from the start.

• Ordering provider identity – the name and NPI of the licensed provider who ordered the test must appear on the claim and in the lab requisition
• Clinical indication in the chart – a brief note explaining why serum iron was ordered (symptoms, prior CBC results, known diagnosis) must be present in the patient record
• Linked ICD-10-CM code – the diagnosis code on the claim must match a covered indication under NCD 190.18 and reflect the actual clinical situation, not a placeholder code
• Date of service and specimen collection date – must match between the lab report, the requisition, and the claim form
• Lab report retention – the quantitative result must be retained in the patient record to support any retrospective audit request from CMS or a commercial payer

Common denial reasons for CPT 83540 claims include missing ICD-10 linkage, billing for a non-covered routine screening without documentation of clinical necessity, and mismatched specimen dates. Reviewing common denial codes in medical billing before claims go out helps billing staff recognize and correct these errors before submission.

When a denial does occur, tracking remittance adjustment reason codes (CARCs) on the ERA is the fastest way to identify the specific payer objection and determine whether to appeal or correct and resubmit.

How practice management software simplifies iron panel billing

Most CPT 83540 denials are preventable. They occur because the CPT-to-ICD-10 linkage happens manually, at billing time, rather than at order time when the clinical context is freshest. Practice management software that integrates lab ordering, superbill generation, and claim submission in one workflow closes that gap.

Pabau’s claims management software supports CPT code assignment with ICD-10 linkage built into the billing workflow, so the diagnosis code travels with the lab order from the moment of documentation through to claim submission. For practices ordering serum iron panels regularly (internal medicine, functional medicine, and integrative health clinics in particular), this reduces the manual rework that follows a preventable denial.

Pabau integrates with Claim.MD for electronic claims via Claim.MD, the US clearinghouse partner that connects to over 4,000 payers, including CMS Medicare. This means a clean CPT 83540 claim, with the correct ICD-10 code attached, can move from Pabau directly to the payer’s adjudication queue without a separate clearinghouse login or manual file export.

The same integration supports real-time eligibility checks before the patient’s specimen is even collected, which is the cleanest way to confirm Medicare or commercial coverage before the test is ordered.

Supporting revenue cycle management for lab-heavy practices also means handling the back end: ERA posting when remittances come back, tracking claim status, and flagging underpayments. For a code like 83540 where the allowed amount is under $10, the administrative cost of working a manual denial often exceeds the reimbursement itself.

Automation makes it economically viable to appeal, correct, and resubmit rather than write off small-dollar lab claims. Effective denial management processes built into the billing workflow can meaningfully improve net collection rates for practices with high lab claim volume.

Conclusion

CPT code 83540 is a straightforward chemistry code with a narrow reimbursement window, which means billing errors eat directly into already thin margins. Getting the ICD-10 linkage right, understanding NCD 190.18 covered indications, and submitting a clean claim the first time are the three levers practices control.

Practices that automate the CPT-to-ICD-10 pairing at order time, validate eligibility before the specimen is collected, and receive ERA remittances automatically recover more revenue per claim than those managing these steps manually.

Pabau’s integrated clean claim workflow handles CPT assignment, diagnosis linkage, eligibility verification, and clearinghouse submission from a single platform. To see how it works for lab-intensive practices, book a demo.

Continue your research

Want to understand what clearinghouse connectivity actually does for lab claim submission? How a medical claims clearinghouse works explains the full EDI claim path from practice to payer.

Seeing recurring denial codes on your ERA and not sure how to respond? Electronic remittance advice explained covers how to read CARC and RARC codes and decide whether to appeal or resubmit.

Need a framework for evaluating your lab billing compliance posture? Revenue cycle management guide outlines the end-to-end process from eligibility check through payment posting.

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