CPT® Code 97033

Quick Reference

• Code definition: CPT 97033 covers iontophoresis, a constant-attendance physical therapy modality that uses low-level direct electrical current to drive ionized medication transdermally into tissue, billed per 15-minute interval of continuous therapist attendance.
• Key billing rule: Each unit equals one complete 15-minute block of direct, one-on-one therapist contact. Setup and preparation time do not count toward billed units. The Medicare MUE cap is 4 units (60 minutes) per date of service [3].
• Modifier essentials: GP is required on every Medicare line when service is part of an outpatient physical therapy plan of care; GO for occupational therapy. Append KX when the Medicare therapy cap financial threshold is exceeded. Use 59 or XU when billing alongside a same-day re-evaluation (97164 or 97168).
• Documentation must-have: The record must specify the ionic medication used, polarity setup, current intensity, duration of each 15-minute period, and explicit confirmation of constant therapist attendance throughout the entire timed interval.
• Top confusion point: Do not substitute 97014 (unattended electrical stimulation) for 97033. Iontophoresis requires constant attendance and delivers medication via electrical current; 97014 is Status I (not valid for Medicare) and describes a fundamentally different service.
• Payer alert: Medicare caps payment at 4 units per date of service; the MUE adjudication indicator is 3 (Date of Service, Clinical), meaning claims exceeding 4 units are denied at the claim level and no modifier overrides this limit [3].

When to Use This Code

CPT 97033 applies when a licensed therapist personally and continuously attends a patient while using direct electrical current to repel ionic medication through the skin into underlying tissue. The "1 or more areas" language means a single unit covers all body sites treated during that 15-minute block, regardless of how many anatomical locations receive iontophoresis simultaneously. Do not bill additional units for treating multiple areas within the same time interval.

Clinical indications include:

• Tendinitis, bursitis, or plantar fasciitis treated with dexamethasone or hydrocortisone for local anti-inflammatory effect
• Calcific tendonitis managed with acetic acid to promote calcium resorption
• Lateral epicondylitis or shoulder pathology using corticosteroid delivery
• Muscle spasms or myositis treated with magnesium sulfate or calcium chloride
• Adhesive capsulitis with iodine delivery to reduce periarticular stiffness
• Hyperhidrosis of the hands or feet using the tap water tray method (no medication required for this indication)
• Local analgesia via lidocaine delivery before other procedures or for pain management

Scope boundaries: The code applies only when the therapist is physically present and directly attending the patient for the entirety of each 15-minute unit. Electrical stimulation administered while the therapist is attending to other patients or operating equipment without continuous presence falls outside the 97033 framework and may not be separately billable. The service is not reportable via telehealth; CMS does not include physical therapy modalities on the Medicare telehealth services list [4].

Provider and setting: Physical therapists, occupational therapists, podiatrists, dermatologists, and sports medicine providers all report this code within their respective scopes. In outpatient therapy settings, Medicare requires a signed physician or qualified non-physician practitioner plan of care. In facility settings such as SNFs or hospital outpatient departments, the PC/TC Indicator of 7 means Medicare payment may be bundled into the facility's rate rather than paid separately on the professional claim [1].

Unit calculation: Each complete 15-minute block equals 1 unit. A 20-minute session reports as 1 unit; the remaining 5 minutes does not constitute a second unit under standard conventions. A 30-minute session reports as 2 units. Some commercial payers apply the 8-minute rule used for other timed therapy codes; confirm with each payer whether a partial period above 7 minutes qualifies for an additional unit. The 4-unit Medicare MUE cap means 60 minutes per day is the maximum billable amount under Medicare [3].

Code Differentiation Table

The critical differentiator for 97033 specifically: the code requires both electrical current AND a drug delivery intent (or the tap water hyperhidrosis protocol). Electrical stimulation applied without an ionic medication does not meet 97033 criteria; 97032 covers constant-attendance manual electrical stimulation without drug delivery. The constant-attendance requirement also separates all codes in the 97032 to 97039 range from the supervised modality codes in 97010 to 97028 [4].

flowchart TD
    A[Electrical current applied to patient] --> B{Ionic medication or tap water protocol?}
    B -- Yes --> C{Therapist in constant attendance?}
    B -- No --> D[97032 - Electrical stimulation manual]
    C -- Yes --> E[97033 - Iontophoresis]
    C -- No --> F[97014 - Electrical stimulation unattended\nNote: Status I, not valid for Medicare]

Billing and Modifier Rules

GP and GO modifiers: CMS requires GP on every line item when the service is part of an outpatient physical therapy plan of care, and GO when it is part of an outpatient occupational therapy plan of care [1]. A missing discipline modifier on a Medicare claim causes rejection or denial. GN (speech-language pathology plan of care) does not apply to iontophoresis; it is not an SLP modality.

KX modifier: Once a Medicare patient's cumulative therapy charges exceed the annual financial threshold, KX must be appended to certify that services remain medically necessary and that supporting documentation is on file. Claims above the threshold without KX are denied. Billing staff must track cumulative therapy charges per beneficiary and flag claims crossing the threshold before submission.

Modifier 59 and XU: Active NCCI PTP edits exist between 97033 and 97164 (PT re-evaluation) and between 97033 and 97168 (OT re-evaluation); both carry Modifier Indicator = 1 (modifier-overridable), effective 10/01/2020 [5]. When both services are medically necessary and separately documented on the same date, append modifier 59 or XU to bypass the edit. Initial PT evaluations (97161, 97162, 97163) and initial OT evaluations (97165, 97166, 97167) do not carry an active PTP edit with 97033 as of current NCCI tables; confirm against the current version before billing.

Multiple procedures indicator = 5: Special payment adjustment rules apply to the RVU practice expense component when 97033 is billed alongside other therapy services on the same date. This is separate from the standard 50% bilateral or multiple procedure reduction; it affects the PE RVU, not the work RVU [1].

Bilateral modifier 50: Does not apply. The bilateral indicator for 97033 is 0; the "1 or more areas" language already captures multi-site treatment within a single time unit.

Absolute bundling (Modifier Indicator = 0): Four NCCI PTP edits cannot be bypassed under any circumstance [5]:

Same-interval rule: Providers may not report more than one physical medicine and rehabilitation therapy service for the same 15-minute time period. The supervised modality exception that allows overlap applies only to 97010 to 97028; it does not apply to 97033 [4]. When 97033 and another timed therapy service are performed on the same day, they must occupy distinct, non-overlapping time intervals to be separately reportable. Modifier 59 or XU documents this when applicable.

Documentation Essentials

Each 97033 service requires the following in the medical record:

• Type of modality and units performed: Document "iontophoresis" explicitly; record the number of 15-minute units and total treatment duration.
• Ionic substance, concentration, and polarity: Specify the medication (e.g., dexamethasone 4 mg/mL), the electrode polarity (anode for positive ions, cathode for negative ions), and the current intensity in milliamperes.
• Body area treated: Identify each anatomical site receiving treatment (e.g., right plantar fascia, left lateral epicondyle).
• Constant attendance attestation: Documentation must affirmatively reflect that the therapist was in direct, one-on-one contact throughout each timed interval. Entries stating "patient monitored periodically" or "equipment running, therapist available" are inconsistent with 97033 requirements and will support a downcode or denial on audit.
• Patient response and tolerance: Note skin reactions, patient-reported comfort, treatment modifications, and any adverse responses.
• Plan of care linkage: Each service must tie to an active, signed plan of care with documented medical necessity. Medicare requires a POC signed by a physician or qualified non-physician practitioner.
• Treating therapist identity: Name, credentials, and NPI of the treating therapist on every visit note.

Audit red flags: Auditors and RACs flag 97033 claims when documentation reflects group treatment or divided attention among multiple patients; when the same unit count appears on every visit note regardless of stated treatment time; when medication, concentration, or polarity is absent; or when four units are billed daily for extended periods without documented clinical rationale supporting 60 minutes of iontophoresis per session. The MUE adjudication indicator of 3 means appeal of a greater-than-4-unit denial requires documentation of extraordinary clinical circumstances, but the MUE itself cannot be overridden by modifier [3].

Medicare, Commercial and Medicaid Payer Rules

Medicare:

CPT 97033 carries Status A (active, separately payable) under the Medicare Physician Fee Schedule for both facility and non-facility settings [1]. The 2026 non-facility Medicare payment rate is approximately $19.04 per unit, based on a total RVU of 0.57 multiplied by the 2026 conversion factor of $33.4009 [6]. The non-facility PE RVU decreased slightly from 0.31 (2025) to 0.30 (2026); work RVU remains at 0.26. The APC Status Indicator confirms payment under the PFS rather than OPPS for most outpatient settings.

MUE = 4 units per date of service, effective 04-01-2026; MAI = 3 (Date of Service, Clinical) [3]. No nationally applicable LCD specific to CPT 97033 was confirmed from CMS national resources. Individual MACs (CGS, Noridian, Novitas, Palmetto, NGS, WPS) may maintain active physical therapy LCDs that set coverage criteria and frequency limits; verify current MAC LCD status at the CMS Medicare Coverage Database for your jurisdiction. No OIG Work Plan item specifically targeting 97033 or iontophoresis was identified as of the January 2026 update, though outpatient physical therapy fraud and abuse remains an ongoing OIG concern area [7].

Home health billing carries additional constraints: G0151 (PT services in home health), G0157, and G0159 (PT/OT assistant home health codes) have active NCCI edits with 97033 (Modifier Indicator = 1) [5].

Commercial payers:

Commercial policies vary in coverage criteria, prior authorization requirements, and session frequency caps for iontophoresis. Some payers restrict coverage to specific diagnosis codes or require documented failure of conservative measures. The 8-minute rule for partial unit calculation is a Medicare construct; commercial payers may apply different rounding conventions. Verify current payer policy before assuming Medicare billing rules govern commercial claims.

Medicaid:

State Medicaid programs generally follow Medicare coverage logic but may require prior authorization for physical therapy services above a defined visit threshold. Managed Medicaid plans may impose their own frequency caps or require TAR (treatment authorization request) for extended episodes of care. No state-specific coverage variations for 97033 were identified in the research sources; consult your state Medicaid fee schedule and applicable MCO contracts directly.

Common Denials and Prevention

Exceeding MUE: more than 4 units per date of service CMS automatically denies claims where 97033 units exceed 4 on a single date of service. The clinical MAI of 3 means this edit is applied at the claim level without modifier bypass. Document exact treatment start and stop times for each unit to ensure accuracy. If extraordinary clinical circumstances require more than 60 minutes in a day, retain documentation for potential appeal, but denial should be anticipated.

Missing therapy discipline modifier Medicare claims submitted without GP or GO are rejected or denied at the line level. Implement a billing edit or charge capture rule to flag any 97033 line missing the appropriate discipline modifier before submission. Every line on every Medicare claim requires the modifier, not just the first line.

NCCI edit denial: 97033 billed with 97164 or 97168 without modifier When a re-evaluation and iontophoresis occur on the same date, the NCCI PTP edit triggers [5]. Submit modifier 59 or XU on 97033 to indicate a distinct, non-overlapping service. Retain separate, contemporaneous documentation for both services. Do not append the modifier if the services did not genuinely occur as independent, separately documented clinical events; doing so constitutes a false claim.

Insufficient documentation for constant attendance Post-payment auditors target 97033 claims when notes reflect passive equipment monitoring rather than active therapist presence. If the visit note does not affirmatively document continuous, one-on-one contact throughout the timed period, the service does not meet the code requirements and is subject to recoupment. Train therapists to document attendance explicitly in every visit note, not just on initial encounters.

Missing KX modifier above therapy cap Claims above the annual Medicare therapy cap threshold are denied without KX. Billing staff must track cumulative therapy charges per beneficiary across all disciplines and flag claims crossing the threshold. A missing KX error is recoverable through a corrected claim if identified promptly; after the timely filing window, the loss is permanent.

Coding Scenarios

Scenario 1: Plantar fasciitis, standard session A physical therapist applies iontophoresis with dexamethasone 4 mg/mL to a patient's right plantar fascia for 20 minutes under continuous, one-on-one attendance. The patient is covered under Medicare Part B with an active outpatient PT plan of care.

Correct coding: 97033 GP x1 unit

Why: One complete 15-minute block was delivered; the remaining 5 minutes does not constitute a second unit. GP is required on all Medicare outpatient PT claims. Confirm payer-specific rounding policy if the partial period exceeds 7 minutes and the payer applies the 8-minute rule.

Scenario 2: PT re-evaluation and iontophoresis on the same day An established Medicare patient returns for a PT re-evaluation of their rotator cuff tendinitis plan of care. After completing the re-evaluation, the therapist performs 30 minutes of iontophoresis with dexamethasone to the right shoulder under constant attendance. Both services are separately documented.

Correct coding: 97164 GP, 97033 GP XU x2 units

Why: The NCCI PTP edit between 97033 and 97164 (Modifier Indicator = 1, effective 10/01/2020) requires a modifier when both are billed on the same date [5]. Modifier XU documents that the re-evaluation and the modality were distinct, non-overlapping services. Separate clinical documentation for each service is required to support the modifier.

Scenario 3: Hyperhidrosis, bilateral hands, dermatology setting A dermatologist uses the tap water tray method to administer iontophoresis to both hands simultaneously for 30 minutes to treat palmar hyperhidrosis. The patient has commercial insurance only.

Correct coding: 97033 x2 units (no discipline modifier)

Why: Two complete 15-minute blocks were delivered. Bilateral modifier 50 does not apply; the "1 or more areas" descriptor covers multisite treatment within each time block. No GP or GO modifier applies because the billing provider is a dermatologist reporting a medical service under their own scope, not under a therapy plan of care.

Scenario 4: Above Medicare therapy cap, chronic tendinitis A Medicare patient with chronic rotator cuff tendinitis has exceeded the annual therapy cap financial threshold. The treating PT continues medically necessary iontophoresis with dexamethasone at each visit, with supporting documentation on file.

Correct coding: 97033 GP KX x units performed per visit

Why: KX certifies that documentation supports medical necessity for services above the threshold [1]. Claims submitted without KX after the threshold is crossed are denied. The PT must confirm the supporting clinical record is current and complete before appending KX; the modifier represents a certification of record content, not just a billing flag.

Related Codes

• 97032 — Electrical stimulation (manual), each 15 minutes: constant-attendance timed modality in the same subrange as 97033; no drug delivery
• 97035 — Ultrasound, each 15 minutes: constant-attendance timed modality; MUE 2; commonly billed alongside 97033 in distinct time intervals
• 97034 — Contrast bath, each 15 minutes: constant-attendance timed modality; MUE 2
• 97010 — Hot or cold packs: supervised modality; Status B (bundled) under Medicare; no constant attendance requirement; often used in the same session
• 97014 — Electrical stimulation (unattended): supervised modality; Status I for Medicare; the most common incorrect code substitution for 97033
• 97164 — Re-evaluation of PT plan of care: active NCCI PTP edit with 97033 (MI=1); modifier 59 or XU required on same-date claims
• 97168 — Re-evaluation of OT plan of care: active NCCI PTP edit with 97033 (MI=1); modifier 59 or XU required on same-date claims
• 97161 — Physical therapy evaluation, low complexity: commonly performed on the same date as first iontophoresis session; no active NCCI PTP edit with 97033 as of current tables

Sources

1. CMS 2026 National Physician Fee Schedule Relative Value File, January Release — CMS, released 12/29/2025. 2026 RVUs, status codes, PC/TC indicators, and payment indicators for 97033.
2. CMS 2025 National Physician Fee Schedule Relative Value File, January Release — CMS, released 12/23/2024. 2025 RVU baseline for year-over-year comparison.
3. CMS NCCI MUE Practitioner Services Table, effective 04-01-2026 — CMS. MUE = 4 units, MAI = 3 (Date of Service, Clinical) for CPT 97033.
4. CMS NCCI Policy Manual Chapter XI, Physical Medicine and Rehabilitation, rev. 1/1/2026 — CMS. Constant-attendance vs. supervised modality distinction and same-interval prohibition.
5. CMS NCCI PTP Physician/Practitioner Edits v32.1 r0 — CMS. PTP edit pairs for 97033 including 36591, 36592, 96523, 0583T, 97164, and 97168.
6. CY 2026 PFS Final Rule, Federal Register — Federal Register / CMS, published 11/28/2025. CY 2026 conversion factor ($33.4009) and payment policy changes.
7. HHS OIG Work Plan — HHS OIG, modified 2026-01-16. No active work plan item identified specifically for CPT 97033 or iontophoresis; outpatient PT fraud and abuse remains an ongoing OIG concern area.