CPT code 80400 – ACTH stimulation panel billing guide

Key takeaways

CPT code 80400 is the ACTH stimulation panel for adrenal insufficiency, and it includes two total cortisol measurements (82533 x2).

Plasma ACTH (82024), the cosyntropin itself (J0834), its injection (96372 or 96374) and venipuncture (36415) all sit outside the panel.

Billing CPT 82533 as a separate line next to 80400 triggers an NCCI bundling edit and is the most common denial cause.

ICD-10-CM E27.1 (primary adrenocortical insufficiency) and E27.40 (unspecified adrenocortical insufficiency) are the most widely accepted diagnoses, though coverage varies by MAC.

In Pabau, our practice management platform, each 80400 charge carries its linked diagnosis, and the claim goes out through Claim.MD with its status tracked.

CPT code 80400: Official descriptor and clinical overview

CPT code 80400 is the ACTH stimulation panel for adrenal insufficiency. The American Medical Association descriptor reads “ACTH stimulation panel; for adrenal insufficiency,” and the panel must include two total cortisol measurements (82533 x2). The code sits in the Evocative/Suppression Testing subsection of CPT (80400-80439). Those panels capture the lab work in hormonal challenge testing as one code, so the analytes are not billed one by one.

A resting cortisol level is often inconclusive when a physician suspects adrenal insufficiency. Giving synthetic adrenocorticotropic hormone (ACTH) and measuring the adrenal response shows how much reserve the gland has. The AMA’s CPT code set captures that two-specimen workflow as a single panel, so each cortisol draw is not billed on its own.

The subsection placement matters because every Evocative/Suppression Testing panel follows the same rule. Each panel includes only the analytes its descriptor lists. A test outside that list, or a service such as the drug or the injection, is coded on its own line.

What the ACTH stimulation test measures and how it works

The ACTH stimulation test evaluates the hypothalamic-pituitary-adrenal (HPA) axis. It measures how much cortisol the adrenal glands produce after a standardized dose of cosyntropin. Cosyntropin (Cortrosyn) is synthetic ACTH that stimulates the adrenal cortex directly, bypassing the pituitary. Alongside other tests, that helps separate primary from secondary adrenal insufficiency.

The standard short protocol runs as follows:

1. Baseline draw: Serum cortisol collected before cosyntropin administration (time 0).
2. Cosyntropin injection: 250 mcg IV or IM administered immediately after the baseline draw.
3. Stimulated draw: Serum cortisol collected at 30 or 60 minutes post-injection (or both, depending on protocol).
4. Interpretation: A peak cortisol response generally above 18-20 mcg/dL is considered a normal adrenal reserve, though laboratory-specific assay thresholds vary.

CPT 80400 captures two cortisol specimens, matching the baseline-plus-one-stimulated-draw protocol. If the provider collects a third cortisol specimen (baseline, 30 minutes and 60 minutes), that third draw is not separately billable under 80400. Code 80402 does not cover it either. 80402 is “ACTH stimulation panel; for 21 hydroxylase deficiency,” which measures cortisol x2 plus 17-hydroxyprogesterone x2.

CPT 80400 code details at a glance

Use the reference table below for quick-access billing details. The AAPC Codify CPT lookup provides additional code descriptor and crosswalk data for clinical coding teams.

What CPT 80400 includes and what it excludes

Getting the bundle boundaries right prevents the most expensive denial category on this code. The panel includes exactly what its descriptor states. One test can still put up to six codes in front of the biller, and only one of them is the panel.

Included in the panel

• CPT 82533 (cortisol total): Bundled. The descriptor includes cortisol x2, so both measurements in the stimulation sequence are captured by 80400. Billing 82533 on a separate claim line alongside 80400 triggers an NCCI edit and will deny.

Not included: bill separately when performed

• CPT 82024 (ACTH plasma): Plasma ACTH is not part of the 80400 descriptor. Bill it separately when it is performed as part of the workup.
• CPT 82530 (cortisol free): Free cortisol is a distinct analyte from total cortisol. Bill it separately if ordered.
• Cosyntropin (HCPCS J0834, cosyntropin, 0.25 mg): The drug is not bundled into the lab panel. Report it on its own line when the practice supplies it.
• Cosyntropin administration (CPT 96372 or 96374): Report 96372 for an intramuscular injection or 96374 for an IV push.
• Venipuncture (CPT 36415): Specimen collection is not part of the panel, which covers only the cortisol analytes. Bill the draw according to each payer’s rules.
• E&M service: If the ordering physician also sees the patient on the same date, bill the E&M separately with modifier -25 when appropriate.

Related CPT codes for adrenal and cortisol testing

The evocative panels for adrenal testing form a family with the single-analyte cortisol codes. Knowing where each one starts and stops prevents upcoding and downcoding errors.

80400 and 80402 differ by indication and by the extra analyte. 80402 is the panel “for 21 hydroxylase deficiency,” and it adds two 17-hydroxyprogesterone (17-OHP) measurements to the two cortisol results. When the provider orders that panel to evaluate congenital adrenal hyperplasia, 80402 is the correct code.

Bill 82533 on its own only when a total cortisol level is drawn without a stimulation test. Inside a stimulation test, the panel code carries the cortisol results.

ICD-10 codes that support medical necessity for CPT 80400

Every CPT 80400 claim needs a diagnosis code that tells the payer why the ACTH stimulation test was clinically necessary. Local Coverage Determinations (LCDs) from Medicare Administrative Contractors list the ICD-10-CM codes each MAC accepts. Coverage varies by jurisdiction, so confirm your MAC’s active LCD before submission.

Coverage for E27.1 and E27.40 is broadly consistent across MACs, though that assessment should be verified against your jurisdiction’s current LCD. Use the most specific code supported by documentation. Submitting E27.40 when the chart clearly documents Addison’s disease is under-coding and may draw audit scrutiny.

Medicare and insurance reimbursement for CPT 80400

Medicare reimburses CPT code 80400 under the Clinical Laboratory Fee Schedule (CLFS), not the Physician Fee Schedule. CMS updates the CLFS rates every year. To find the current payment amount, download the annual public use file from the CMS Clinical Laboratory Fee Schedule page and look up 80400.

Key reimbursement considerations for this panel:

• CLFS, not PFS: Lab panel codes reimburse at a flat CLFS rate. There are no work, practice expense, or malpractice RVU components.
• Prior authorization: Medicare does not routinely require prior authorization for 80400, but commercial payers increasingly do. Check payer-specific policies each plan year; requirements vary by carrier and market.
• Frequency limitations: Some MACs apply frequency limits (e.g., once per rolling 12-month period) for routine adrenal testing. Document clinical justification when repeating the test within a short interval.
• Commercial reimbursement: Commercial payers often reimburse at a percentage of the Medicare CLFS rate or at independently negotiated rates. Obtain your contracted rate from your payer agreement rather than relying on Medicare figures.

Pabau sends electronic claims through Claim.MD, our US clearinghouse partner, and tracks each claim’s status after submission.

Documentation requirements before billing CPT 80400

Thin documentation is a common trigger for 80400 audits and retrospective recoupments. Medical billing compliance for lab panels requires the chart to support both the order and the result. These elements must be in the chart before the claim goes out:

1. Clinical indication: The chart note must document the signs or symptoms driving the order, such as fatigue, hypotension, hyponatremia, hyperpigmentation or weight loss. A relevant history counts too: steroid use, pituitary disease, or prior adrenal surgery.
2. Morning cortisol context: If a morning serum cortisol was drawn before the stimulation test was ordered, document the value. Explain why it was inconclusive, or why the stimulation test was still warranted.
3. Ordering provider signature and credentials: The ordering provider must be identified and credentialed. Lab panels ordered by unlicensed staff without a supervising provider’s order are non-covered.
4. Cosyntropin dose, route, and time: Record 250 mcg IV or IM, the administration time, and the person who administered it.
5. Specimen collection times: Document the exact draw time for each cortisol specimen. 80400 covers two, so record any extra draw and the reason it was taken.
6. Laboratory result: The completed result, including reference range and units, must be in the chart and reconcilable with the claim date of service.

A clean claim has every required field populated and an explicit diagnosis-to-procedure link. Payers auditing ACTH stimulation claims compare the clinical note date with the lab date. A specimen collected before the order is documented raises a red flag.

Common claim denial reasons for CPT 80400 and how to fix them

A solid denial management workflow starts with the most predictable triggers. The table maps each denial to its root cause and fix.

Match each CARC in remittance advice denial codes to its scenario. CO-97 and CO-234 mean the service is not paid separately, which points to bundling. CO-18 marks a duplicate claim. CO-11 or CO-50 means the payer did not accept the diagnosis as covered.

Each CARC has its own appeal path, so record it at posting time. Read the remittance line by line too. A payer can pay the panel and still deny a companion code, such as the drug or the injection.

How claims management software keeps 80400 claims clean

A panel code like 80400 needs setup steps that single-analyte lab codes do not. Getting charge entry right the first time prevents the denials above.

1. Build 80400 as a single charge item. Bill 80400 as a single line, and do not add 82533 lines. The panel descriptor already contains 82533 x2.
2. Attach the linked diagnosis code at charge entry. Configure your PMS to require an ICD-10-CM code for every 80400 charge before the charge can be saved. E27.1 or E27.40 should be the default options presented, with other covered codes available as alternatives.
3. Review encounters that carry both 80400 and 82533. That pair is the most common denial on this code, so check it before submission. Add the drug, injection and venipuncture lines your payer accepts.
4. Verify prior authorization status before the DOS. For commercial payers that require PA, the authorization number must be on the claim. Create a task that flags 80400 orders for eligibility and PA checks 24-48 hours before the test.
5. Confirm place of service. If you send specimens to a reference lab, confirm whether the lab bills the panel itself or you bill globally. When the lab bills, your claim covers the collection and your POS is 11 or 22.

Without diagnosis linking, a biller checks each 80400 charge against the chart and the LCD list by hand. Pabau’s claims management software attaches the diagnosis code at charge entry instead.

The claim then goes out electronically through Claim.MD, and your billers track its status from the same patient record. Fewer claims leave without a medical-necessity code, and fewer come back as denials to work.

Send clean 80400 claims and track each one

Pabau’s claims management software links the diagnosis to each 80400 charge and sends the claim through Claim.MD. Your billing team then tracks every claim’s status in one place.

Book a demo

Conclusion

Treat 80400 as one line that already holds both cortisol results, and decide the drug, the injection and the draw around it. Before each claim goes out, check the diagnosis against your MAC’s LCD list. Those two habits close off the denials this code is known for.

The trade-off is a few minutes more at charge entry for fewer appeals later. Book a demo to see how Pabau links diagnoses to lab panel charges and tracks each claim through Claim.MD.

Continue your research

Need to understand how claims move through the clearinghouse? Our Claim.MD clearinghouse guide explains the end-to-end submission and adjudication process for US lab claims.

Looking for the 837P file format used to transmit 80400 claims? 837 file format for medical billing covers the transaction set structure and common field-mapping errors.

Want a framework for reducing denials across all lab codes? Revenue cycle management in healthcare outlines the upstream steps that prevent downstream denial volumes.

Frequently asked questions