Phosphorus (Inorganic Phosphate) Blood Test
CPT 84100
Ordered to monitor kidney disease and dialysis patients, or to investigate abnormal calcium levels and bone-mineral disorders.
No national payment amount
Status X is not separately payable under the PFS.
Did Medicare pay separately for CPT 84100 in Q1 2026?
Not at a published national rate. CPT 84100 carries status X (statutory exclusion) in the Q1 2026 release. The statutory definition of physician services does not include this item. Treat the blank amount as unpriced, not as $0.
How often 84100 is billed
Across Original Medicare in CY2024, 84100 ranked #174 of the 7,879 CPT codes billed to Medicare that year, ranked by patients served or total allowed dollars. Patients who received it in 2024 were billed for it an average of 2.0 times that year — more than once per patient.
2024 Medicare fee-for-service only, national totals — Medicare Advantage, Medicaid and commercial volume are excluded, so real-world use runs higher. This is a calendar-year snapshot from the CMS Physician & Other Practitioners dataset, on a different cycle from the Q1 2026 fee schedule the rates above come from.
Common questions
Why is there no payment amount for 84100?
Its status indicator is X (statutory exclusion). The statutory definition of physician services does not include this item. The blank is deliberate: the amount is either unknown or paid under another provision, so reading it as $0 would be wrong.
Why would a Medicare claim for 84100 be denied or paid less?
Each item below comes from a CMS indicator on this page — not general billing advice.
- Its status indicator is X (statutory exclusion) — The statutory definition of physician services does not include this item. See status indicators
Payer-specific coverage and documentation rules live outside these files, so a claim that clears every check here can still be denied on other grounds.
When does this rate change?
CMS publishes a fee schedule release every quarter (January, April, July, October), and each is versioned here. See what changed each release, or get an email when a new release moves rates.
Sources: CMS Medicare Physician Fee Schedule Relative Value Files.
Saw this code on your bill?
What is a 84100 visit in patient-friendly terms?
In plain terms: Measures inorganic phosphate in the blood. Phosphate is cleared by the kidneys and regulated in tandem with calcium, vitamin D, and parathyroid hormone, so it climbs as kidney function fails and falls with malnutrition, with overactive parathyroid glands, and in the first days of feeding someone who has been starved. It is a routine part of monitoring people with chronic kidney disease and those on dialysis, where a persistently high level drives bone and blood-vessel damage. Think of a dialysis patient whose bloods are checked on a regular cycle, with phosphate binders and diet adjusted according to this number. It also gets checked when calcium comes back abnormal, since the two are managed together. You'll typically see CPT 84100 on a bill or explanation of benefits (EOB) when a clinician performs or bills for this service.
How this amount is computed
amount = (work RVU × work GPCI + PE RVU × PE GPCI + MP RVU × MP GPCI) × conversion factor. National amounts use GPCI = 1.000. To price an RVU figure of your own, use the RVU-to-dollars converter.
| Component | RVU |
|---|---|
| Work RVU | blank |
| Practice expense RVU (non-facility) | blank |
| Practice expense RVU (facility) | blank |
| Malpractice RVU | blank |
Every rate combines three parts: work (the clinician’s time, skill and effort), practice expense (office overhead — higher when the service is done in a doctor’s own office), and malpractice (the share of liability-insurance cost). A blank means CMS publishes no national number for that part. Read it as unknown, and never as zero.
Rate history by release
National non-facility amount for 84100 across quarterly releases.
| Release | Status | Non-facility | Facility |
|---|---|---|---|
| Q3 2026 Jun 30, 2026 – present | X | — | — |
| Q2 2026 Mar 10, 2026 – Jun 29, 2026 | X | — | — |
| Q1 2026 Dec 29, 2025 – Mar 9, 2026 | X | — | — |
| Q4 2025 Sep 11, 2025 – Dec 28, 2025 | X | — | — |
| Q3 2025 Jun 5, 2025 – Sep 10, 2025 | X | — | — |
| Q2 2025 Jun 5, 2025 – Jun 4, 2025 | X | — | — |
| Q1 2025 Dec 23, 2024 – Jun 4, 2025 | X | — | — |
Did this answer your question about CPT 84100?
We're building this out in the open. Tell us what you were actually trying to work out and we'll either answer you directly or build the page that does.
Source & method
This is computed from CMS's Medicare Physician Fee Schedule Q1 2026 release (schedule pfs, effective January 2026). National amounts apply a GPCI of 1.000 and leave sequestration off. The status indicator decides payability, never the RVU values, so a blank RVU stays blank. Releases are immutable: a rate retrieved for a past quarter always reflects that release. Commercial and cash-pay figures anywhere on this page are arithmetic on the Medicare amount, using commonly cited reimbursement ranges. They're illustrative, and no nationwide claims database stands behind them.
Description written from primary sources: CMS Medicare Physician Fee Schedule Relative Value Files. Not derived from AMA CPT descriptor text.
Conversion factor $33.4009 read from the same file, row 11, column 26.
Use the (i) buttons next to each amount above for the exact row, columns, and math.
Cite this rate
This link keeps pointing at the Q1 2026 figures, even after a newer release lands.
CPT 84100 Medicare Physician Fee Schedule rate (Q1 2026). Localis. https://localishealth.com/cpt/84100/2026/A