Botox / OnabotulinumtoxinA — Chronic Migraine Only, and What the Documentation Actually Requires
Botox requires G43.7xx, PREEMPT protocol documentation, and two oral preventive failures — submitting under an episodic code produces automatic denial.
PA impact: This card directly affects prior authorization outcomes. Documentation language from this card can be used in PA letters and appeals.
Chronic migraine is the only indication — and the ICD-10 code has to prove it. OnabotulinumtoxinA (Botox) is FDA-approved exclusively for chronic migraine, defined as 15 or more headache days per month for at least three months, with at least eight of those days meeting migraine criteria. Episodic migraine patients do not qualify regardless of severity. The ICD-10 code on the PA must be G43.7xx (chronic migraine). A request submitted under G43.0xx or G43.1xx (episodic codes) will be denied even if the clinical note describes chronic migraine.
The PREEMPT protocol is not optional. Medicare LCD DL39909 (effective February 2026) and most commercial payers require documentation of the exact PREEMPT injection protocol: 155 units across 31 fixed anatomical sites. Acceptable muscles are limited — frontalis, corrugator, procerus, occipitalis, temporalis, trapezius, cervical paraspinals. The protocol is not a general Botox injection; it's a specific, mapped procedure. If you administer Botox for chronic migraine, document that the PREEMPT protocol was followed, name the muscles injected, and note the total units. "Botox 155 units per PREEMPT protocol" in the procedure note is the minimum acceptable documentation.
Step therapy requirements and the stopping rule. Most payers require failure of two oral preventive medication classes before approving Botox — same standard as CGRP preventives. Document each class with agent, dose, duration, and reason for discontinuation. Kaiser and some other commercial payers additionally require documented failure of a CGRP mAb before approving Botox. If approval is granted, Botox is authorized in 12-week cycles with reauthorization required every 2–3 cycles. Many payers apply a "stopping rule": if headache frequency does not improve by at least 50% after two complete injection cycles (24 weeks), the payer may deny continued treatment. Document response objectively at each cycle.
Botox plus CGRP combination is supported but contested. The 2021 AHS Consensus Statement supports combination onabotulinumtoxinA plus CGRP preventive for patients with partial response to either therapy alone. Most payers deny this combination on first submission. Document the specific partial response to each individual therapy with frequency and disability data, then appeal citing the AHS position and two-mechanism rationale.
Waste documentation is required under Medicare. Botox comes in 200-unit vials; PREEMPT protocol uses 155 units. The 45-unit remainder is waste. CMS requires a JW modifier on the claim for wasted units. Failure to document waste can trigger overpayment recovery. The Vault's Medicare Botox template includes the JW modifier reminder.
Provider type and procedure billing. NPs and PAs administer Botox for chronic migraine under the same PREEMPT protocol and PA documentation standards as physicians. The billing difference is procedural: in some state/payer configurations, NPs in supervisory-practice states must bill the injection under the supervising physician's NPI. Check state scope-of-practice and payer-specific billing rules before the first injection.
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Run a PA — free →Citations: FDA onabotulinumtoxinA label (chronic migraine indication) | PREEMPT 1 and 2 trials — Aurora SK et al., Cephalalgia 2010;30(7):793-803 | Medicare LCD DL39909 (effective February 15, 2026) | AHS Consensus 2021 — Ailani J et al., Headache 2021;61(7):1021-1039. doi:10.1111/head.14153.