Modifier Q1 is a HCPCS Level II modifier used to identify routine clinical services furnished to a Medicare beneficiary participating in an approved clinical research study.

Unlike Modifier Q0, which identifies the investigational item or service, Modifier Q1 is reported for routine patient care that would ordinarily be provided even if the patient were not enrolled in the clinical trial.

Modifier Q1 became effective January 1, 2008, replacing the former HCPCS clinical trial modifiers used before CMS standardized clinical research billing. It supports Medicare’s National Coverage Determination (NCD) for routine costs in qualifying clinical trials. (cms.gov)

Modifier

Q1 (Q followed by the numeral one)

Modifier Name

Routine Clinical Service Provided in a Clinical Research Study That Is in an Approved Clinical Research Study

Plain English Explanation

Modifier Q1 tells Medicare:

“This is a routine medical service provided to a patient participating in an approved clinical trial. The service itself is not investigational.”

Purpose

Modifier Q1 is used to:

Identify routine clinical care.
Distinguish routine services from investigational services.
Support Medicare clinical trial billing.
Comply with CMS National Coverage Determination (NCD) 310.1.
Ensure appropriate reimbursement for covered routine costs.

Understanding Modifier Q1

Routine clinical services include healthcare that would normally be provided whether or not the patient is participating in a clinical trial.

Examples include:

Office visits
Hospital visits
Laboratory tests
X-rays
Routine blood work
Electrocardiograms (ECGs)
Standard imaging
Administration of approved medications
Monitoring for treatment response
Follow-up visits related to the covered condition

These services are not the subject of the research study but are medically necessary for patient care.

When to Use Modifier Q1

Append Modifier Q1 when:

The patient is enrolled in an approved Medicare clinical trial.
The service represents routine patient care.
The service is otherwise covered by Medicare.
The service is not investigational.
The claim meets CMS clinical trial billing requirements.

Common examples include:

CPT Code	Description
99213	Office visit
80053	Comprehensive metabolic panel
93000	Electrocardiogram
71046	Chest X-ray
36415	Venipuncture

These services may be billed with Modifier Q1 when furnished as routine care during an approved clinical research study.

When NOT to Use Modifier Q1

Do not use Modifier Q1 when:

The service itself is investigational.
The patient is not enrolled in an approved clinical trial.
The service is experimental.
Medicare does not cover the service.
The payer does not recognize Medicare clinical trial billing rules.

For investigational items or services, report Modifier Q0 instead.

Medicare Rules

Medicare requires:

The study must qualify under Medicare’s clinical trial policy (NCD 310.1) or another applicable CMS coverage policy.
Modifier Q1 identifies routine clinical services.
Clinical trial claims commonly include:
- Modifier Q1
- ICD-10-CM Z00.6 (when applicable)
- Clinical Trial Number (NCT) or other required identifier
Routine costs are covered only if they meet Medicare’s coverage requirements and are not paid by another entity. (cms.gov)

Commercial Insurance Rules

Commercial payer policies vary.

Some commercial insurers:

Follow Medicare clinical trial billing guidelines.
Require prior authorization.
Require sponsor agreements.
Have their own research billing policies.

Always verify payer-specific requirements.

Documentation Requirements

Documentation should include:

Clinical trial enrollment documentation.
Physician order.
Medical necessity.
Evidence that the service is routine care.
Clinical Trial Number (NCT), when required.
Patient consent documentation.
Complete medical record.
Provider signature.

Real Billing Examples

Example 1 – Office Visit

A Medicare beneficiary enrolled in an approved oncology clinical trial returns for a medically necessary follow-up office visit.

Billing

CPT 99213-Q1
ICD-10-CM Z00.6 (when applicable)
Cancer diagnosis

Example 2 – Laboratory Testing

Routine laboratory monitoring is required during participation in the clinical trial.

Billing

Appropriate laboratory CPT code
Modifier Q1

Example 3 – Electrocardiogram

A routine ECG is performed to monitor the patient’s cardiac status during the study.

Billing

CPT 93000-Q1

Example 4 – Imaging

A routine chest X-ray is performed according to the patient’s standard treatment plan during the study.

Billing

CPT 71046-Q1

Example 5 – Incorrect Billing

An investigational implantable device is billed with Modifier Q1.

This is incorrect because investigational items should be reported with Modifier Q0.

CMS-1500 Claim Example

Field	Example
CPT	99213
Modifier	Q1
Diagnosis	Z00.6 + applicable medical condition
Item 19/23	Clinical Trial Number (when required)
Units	1

Common Denials

Missing Modifier Q1.
Patient not enrolled in an approved clinical trial.
Missing Clinical Trial Number.
Missing ICD-10-CM Z00.6 when applicable.
Service incorrectly classified as routine.
Incomplete documentation.

Correcting Denials

Verify the patient was enrolled in an approved clinical trial.
Confirm the service qualifies as routine care.
Add Modifier Q1.
Include the Clinical Trial Number if required.
Report ICD-10-CM Z00.6 when applicable.
Submit a corrected claim with supporting documentation.

Coding Tips

Q1 = Routine Care
Q0 = Investigational Service
Do not interchange Q0 and Q1.
Include required clinical trial identifiers.
Maintain complete research documentation.
Review CMS clinical trial billing updates regularly.

Modifier Q1 vs Modifier Q0

Modifier	Description
Q1	Routine clinical service during an approved clinical trial
Q0	Investigational item or service being studied

Modifier Q1 vs Modifier QW

Modifier	Description
Q1	Routine clinical trial service
QW	CLIA-waived laboratory test

Modifier Q1 vs Modifier 95

Modifier	Description
Q1	Routine clinical trial care
95	Telehealth service provided via real-time interactive audio and video

Frequently Asked Questions (FAQs)

Q1. What does Modifier Q1 mean?

Answer: It identifies a routine clinical service provided during an approved clinical research study.

Q2. What is the difference between Q0 and Q1?

Answer: Q0 is used for the investigational item or service, while Q1 is used for routine patient care furnished during the approved clinical trial.

Q3. Is ICD-10-CM Z00.6 reported with Q1?

Answer: Yes, when applicable to Medicare clinical trial billing, Z00.6 is commonly reported along with the diagnosis for the condition being treated.

Q4. Is a Clinical Trial Number required?

Answer: Yes. Medicare requires the appropriate Clinical Trial Number (NCT) or other required identifier for qualifying claims.

Q5. Can commercial insurance require Modifier Q1?

Answer: Some commercial insurers recognize Modifier Q1, but policies vary. Always verify payer-specific clinical trial billing requirements.

AR Caller Tips

When following up on Q1 claims:

Confirm enrollment in an approved clinical trial.
Verify the service is routine, not investigational.
Check that Modifier Q1 was appended.
Verify the Clinical Trial Number and Z00.6, when applicable.
Document payer representative names, reference numbers, and appeal instructions.

Interview Questions

Question 1

What is Modifier Q1 used for?

Answer: It identifies routine clinical services provided during an approved clinical research study.

Question 2

How is Modifier Q1 different from Modifier Q0?

Answer: Q1 is for routine patient care; Q0 is for the investigational item or service.

Question 3

Can an office visit be billed with Q1?

Answer: Yes, if it is routine care provided during an approved clinical trial and otherwise meets Medicare coverage requirements.

Question 4

What diagnosis code is commonly reported with Q1 claims?

Answer: ICD-10-CM Z00.6, when applicable, in addition to the diagnosis for the condition being treated.

Practice Scenario

Scenario

A Medicare beneficiary enrolled in an approved oncology clinical trial returns for a medically necessary follow-up visit and routine laboratory testing. Neither service is investigational.

Question

How should the services be billed?

Answer

Report:

99213-Q1
Appropriate laboratory CPT code with Q1, if applicable
ICD-10-CM Z00.6 (when required)
Clinical Trial Number (NCT), if required

These services represent routine patient care provided during participation in an approved clinical research study.

Related Medicare Special Modifiers

Q0 – Investigational Clinical Service Provided in an Approved Clinical Research Study
QW – CLIA Waived Test
Q6 – Service Furnished by a Locum Tenens (Substitute) Physician
Q5 – Service Furnished Under a Reciprocal Billing Arrangement

Common Billing Mistakes

Using Q1 for investigational services.
Omitting the Clinical Trial Number.
Forgetting ICD-10-CM Z00.6 when applicable.
Confusing Q1 with Q0.
Billing non-covered routine services.

Key Takeaways

Modifier Q1 identifies routine clinical services provided during an approved clinical research study.
It is distinct from Modifier Q0, which identifies investigational items or services.
Medicare clinical trial claims often require ICD-10-CM Z00.6 and a Clinical Trial Number.
Routine services must still meet Medicare coverage requirements.
Proper documentation and adherence to CMS clinical trial billing rules help prevent denials.

References

CMS MLN Matters MM5805 – New HCPCS Modifiers for Clinical Research Studies. (cms.gov)
CMS Medicare Claims Processing Manual, Chapter 32 – Billing Requirements for Clinical Trials. (cms.gov)
Medicare National Coverage Determination (NCD) 310.1 – Routine Costs in Clinical Trials. (cms.gov)
HCPCS Level II Code Book.
CPT® Professional Edition (American Medical Association).

Conclusion

Modifier Q1 is an essential Medicare HCPCS modifier used to identify routine clinical services provided to beneficiaries participating in approved clinical research studies. It ensures that medically necessary routine care is distinguished from investigational services and billed correctly under Medicare clinical trial policies. Proper use of Modifier Q1, along with required diagnosis codes and clinical trial identifiers, supports compliant billing, minimizes claim denials, and facilitates accurate reimbursement.

Educational Disclaimer

This article was prepared with the assistance of artificial intelligence (AI) for educational and informational purposes. It is based on publicly available CMS guidance, Medicare clinical trial policies, HCPCS Level II guidance, and general medical billing principles. It is not an official publication of CMS or the American Medical Association (AMA). Always consult the latest CMS Medicare Claims Processing Manual, Medicare National Coverage Determination (NCD) 310.1, HCPCS Level II Code Book, CPT® Professional Edition, and payer-specific billing policies before coding, billing, or submitting claims.