CPT (Current Procedural Terminology) codes are five-digit numbers that describe every medical service or procedure. Your doctor, hospital, and insurance company use them to communicate exactly what was done. Every line on your medical bill has a CPT code, and knowing the code lets you look up what Medicare pays for that same service.

Why do providers charge so much more than Medicare pays?

Providers set their own "chargemaster" prices, which are essentially list prices. Medicare pays a fixed rate based on the resources each service actually requires (the RVU system for procedures, or the Clinical Lab Fee Schedule for lab tests). Commercial insurers typically pay 150% to 250% of Medicare rates. Uninsured patients are often billed the full chargemaster price, which can be 2x to 30x what Medicare pays.

Can I use Medicare rates to negotiate my bill?

Yes. Medicare rates are the closest thing to a "fair price" benchmark in U.S. healthcare. When negotiating, ask the provider what they accept from Medicare for the same CPT code. Most providers will accept 150% to 200% of Medicare for cash-pay patients, which is still far less than their chargemaster price. Many hospital financial assistance policies also use a multiple of Medicare as their discount floor.

How are Medicare rates calculated?

For most procedures, Medicare uses the Resource-Based Relative Value Scale (RBRVS). Each CPT code gets three RVU components: Work (physician time and skill), Practice Expense (overhead), and Malpractice. These are multiplied by geographic adjustment factors (GPCIs) and a conversion factor ($33.4009 in 2026). Lab tests (80000-89999 range) use a separate Clinical Laboratory Fee Schedule with flat national rates.

CPT 83540

Serum Iron Level (Iron Blood Test)

CPT 83540 measures the amount of iron circulating in your blood at the time of the draw. It is one of the most commonly ordered lab tests (over 2 million Medicare beneficiaries in 2023). Providers charge an average of $32.40, but Medicare pays only about $5 to $7 under the Clinical Laboratory Fee Schedule. The key thing to know: serum iron alone is not very useful because it fluctuates throughout the day. It is almost always ordered alongside TIBC (83550) to calculate iron saturation.

Updated May 2026Source: CMS Clinical Lab Fee Schedule

CPT 83540 at a Glance

Medicare CLFS rate: ~$5 to $7
Average provider charge: $32.40
Direct-to-consumer (full iron panel): $30 to $50
Usually paired with: TIBC (83550)

What it measures: Circulating serum iron
Beneficiaries (2023): 2,023,937
Fee schedule: Clinical Laboratory (CLFS)
Rate type: National (no geographic adjustment)

How Lab Pricing Works (Clinical Laboratory Fee Schedule)

Unlike physician services that use RVUs and geographic adjustments, lab tests are priced under the Medicare Clinical Laboratory Fee Schedule (CLFS). The CLFS sets a single national rate for each test. There are no geographic cost adjustments. The same serum iron test costs Medicare the same amount regardless of whether the lab is in New York City or rural Arkansas.

Metric	Value
Medicare CLFS Rate	~$5 to $7
Average Provider Charge	$32.40
Markup Ratio	~5x
Pricing Method	National rate (CLFS), no geographic variation

The real cost of an "iron test": Serum iron (83540) is rarely ordered alone. You will typically see it paired with TIBC (83550, avg. $44.16) and possibly ferritin (82728, avg. $77). At average charges, a full iron workup totals about $153 for what patients think of as "one iron test." Through a direct-to-consumer lab, you can get all three for $30 to $50.

Lab tests are priced under the Clinical Laboratory Fee Schedule, not the Physician Fee Schedule. Medicare lab rates are set nationally and do not vary by geographic location.

What Does a Serum Iron Test Measure?

Serum iron measures the amount of iron bound to transferrin (a transport protein) in your blood at that specific moment. It is used to evaluate iron deficiency anemia, iron overload (hemochromatosis), and other blood disorders.

What It Can Detect

Iron deficiency (low iron, leading to anemia)
Iron overload / hemochromatosis (dangerously high iron)
Chronic disease effects on iron metabolism
Response to iron supplementation therapy

Important Limitations

Fluctuates significantly throughout the day (diurnal variation)
Affected by recent meals (eating increases iron transiently)
A single value is unreliable without context from TIBC and ferritin
Should be drawn fasting in the morning for best accuracy

The iron panel explained: Serum iron (83540) tells you how much iron is in your blood right now. TIBC (83550) tells you how much iron your blood could carry. Together, they calculate transferrin saturation (iron divided by TIBC), which is the most useful number for your doctor. Ferritin (82728) tells you how much iron is stored in your body long-term. All three together give a complete picture of iron status.

Where to Get an Iron Test for Less

The price difference between venues is enormous. A full iron panel (iron + TIBC + ferritin) at a hospital can cost $150+ while the same three tests at a direct-to-consumer lab cost $30 to $50:

Direct-to-Consumer Labs (full iron panel): $30 to $50

Services like Quest Diagnostics walk-in, LabCorp patient service centers, Ulta Lab Tests, and Jason Health offer complete iron panels (iron + TIBC + ferritin) for $30 to $50 without a doctor's order in most states. You pay upfront, get drawn at a local lab, and receive results online. This is the best value for iron testing.

Independent Labs (with doctor's order): $15 to $40

If your doctor orders the test, ask for the order to go to Quest or LabCorp rather than a hospital lab. The iron test alone typically costs $10 to $20 at an independent lab. With TIBC added, expect $20 to $40 total.

Hospital Outpatient Labs: $75 to $150+

Hospital labs charge the highest prices. Iron ($32) plus TIBC ($44) plus ferritin ($77) totals $153 at average charges. Some hospitals add specimen collection fees on top. This is 3 to 5 times what you would pay at a direct-to-consumer lab for identical tests.

For HDHP patients: If you have a high-deductible plan and have not met your deductible, a $30 to $50 direct-to-consumer iron panel is almost certainly cheaper than going through insurance (where you would pay the negotiated rate, often $40 to $80, against your deductible). However, cash payments do not count toward your deductible.

What Insured Patients Actually Pay

The good news: Medicare covers lab tests at 100% with no patient coinsurance. For commercial insurance, your cost depends on your plan:

Your Situation	What You Likely Pay	How It Works
Copay plan (deductible met or N/A)	$0 to $10	Many plans cover lab work at 100% after deductible
Coinsurance plan (deductible met)	$1 to $5	20% of negotiated rate ($5 to $25)
High-deductible plan (deductible NOT met)	$5 to $25	Full negotiated rate applied to your deductible
Medicare Part B	$0	Medicare covers clinical lab tests at 100% (no coinsurance)

Common Billing Problems with CPT 83540

Iron ordered without TIBC (incomplete workup billed at full price)

Serum iron alone is clinically limited. If your doctor ordered iron without TIBC, the result may be uninterpretable, and you may need to return for another blood draw to get TIBC (and another charge). If you are being evaluated for iron status, ask your doctor to order the full panel upfront: iron, TIBC, and ferritin. One blood draw, one visit, complete information.

Duplicate charges for iron and TIBC components

Some labs calculate UIBC (unsaturated iron binding capacity) instead of TIBC, using a different CPT code. TIBC can be calculated from iron + UIBC. Make sure you are not charged for both TIBC (83550) and UIBC (a component of TIBC) on the same draw. If you see both, one is redundant.

Hospital facility fee added to lab work

Some hospital outpatient labs add a specimen collection fee or facility fee on top of the test charge. A $32 iron test can become $50 or more after fees. Compare with independent lab pricing, where specimen collection is typically included in the test price.

Related Iron Panel Codes

Code	Description	Medicare CLFS	Avg. Charge
83540	Serum Iron	~$5-7	$32.40
83550	TIBC (Total Iron Binding Capacity)	~$6-8	$44.16
82728	Ferritin (iron stores)	~$11-14	$77.00

Frequently Asked Questions

How much does a serum iron test (CPT 83540) cost without insurance?

Without insurance, a serum iron test costs $20 to $50 at most labs, with the national average charge at $32.40. Direct-to-consumer labs offer a full iron panel (iron, TIBC, and ferritin) for $30 to $50 total. Medicare pays approximately $5 to $7 for the iron test alone under the Clinical Laboratory Fee Schedule.

Why is serum iron almost always ordered with TIBC?

Serum iron by itself fluctuates throughout the day and is affected by recent meals. It needs to be combined with TIBC (CPT 83550) to calculate transferrin saturation, which is a much more stable and clinically useful number. Think of iron as one data point and transferrin saturation as the actual clinical indicator. Without TIBC, your doctor cannot calculate saturation.

What is an iron panel and how much does it cost?

An iron panel typically includes serum iron (83540), TIBC (83550), and ferritin (82728). At average provider charges, these total about $153 ($32.40 + $44.16 + $77). Through direct-to-consumer labs, the same panel costs $30 to $50 for all three tests combined. The price difference is enormous, and the tests are identical regardless of where they are run.

Does Medicare cover serum iron testing?

Yes. Medicare Part B covers clinical lab tests at 100% with no patient coinsurance when ordered with a valid medical indication. You pay nothing out of pocket for covered lab work under traditional Medicare. The test must be medically necessary (for example, evaluating suspected anemia or monitoring iron therapy).

Need Help Lowering a Medical Bill?

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