CPT code 83986: Body fluid pH, other body fluids2026 Medicare lab fee · Clinical Laboratory Fee Schedule
Measures the pH of a body-fluid specimen, commonly pleural fluid evaluated during workup of an effusion or suspected pleural infection.
Medicare pays $3.58 for 83986 under the 2026 Clinical Laboratory Fee Schedule: one national amount, the same in every state and setting.
Medicare lab fee · CLFS 2026 Q4
National CLFS amount
$3.58
In effect since Jan 1, 2026. The same amount in every state, payment locality and setting.
- Geographic adjustment
- None
- Office vs facility
- Same
- Since 2020
- Unchanged
- QW · CLIA-waived test
- $3.58
Medicare pays the lesser of the lab’s charge and this amount. Patients usually owe no Part B deductible or coinsurance for covered clinical lab tests.
On this page 8 sections
What 83986 covers
This assay measures the acidity or alkalinity in a body-fluid specimen. Pleural-fluid pH is a common application during evaluation of a pleural effusion, particularly when a parapneumonic effusion or empyema is considered; results are interpreted with clinical findings and other fluid studies. Laboratories perform the assay on provider-ordered specimens in clinical laboratories. The specimen type distinguishes this assay from testing for exhaled breath condensate.
A CLIA-waived version may be reported with modifier QW at a site holding a CLIA certificate of waiver. Medicare pays 83986 only through the CLFS, at one national amount across states and localities, with no office or facility difference. The 2026 national CLFS amount is $3.58, unchanged since 2020.
This summary was written with AI assistance from CMS Clinical Laboratory Fee Schedule data. Amounts on this page come directly from CMS files.
How Medicare pays 83986
Clinical lab tests aren’t priced like physician services. They’re paid from their own fee schedule, with its own rules. See the whole lab fee schedule.
One national amount
CMS sets a single Clinical Laboratory Fee Schedule amount for 83986. There’s no geographic (GPCI) adjustment, so it pays the same in every state and payment locality.
No office or facility rate
Lab tests aren’t built from relative value units, so there’s no office and facility split: the place of service doesn’t change the CLFS amount.
Updated every quarter
CMS republishes the CLFS each quarter. New tests, often proprietary laboratory analyses (PLA codes), join during the year; existing amounts are updated each January.
Excluded from the physician fee schedule
The physician fee schedule lists 83986 with status X (excluded by statute), so the test itself is paid only from the CLFS.
CLIA-waived version (QW)
CMS also lists 83986 with modifier QW, the version labs holding a CLIA certificate of waiver bill. It pays $3.58.
83986 on the lab fee schedule since 2020
83986 · CLFS 2026 Q4 (current)
$3.58
Unchanged since Jan 1, 2020
27 quarterly CLFS releases on file, first CLFS 2020 Q1. A code missing from a quarter wasn’t on that release.
83986 compared with similar tests
- 83987Breath condensatepH measurement$3.58
- Use 83987 for pH testing of exhaled breath condensate. Use 83986 for pH testing of body fluid.
- 81003UrinalysisAutomated, without microscopy$2.25
- Code 81003 describes automated urinalysis without microscopy, including reagent-strip testing such as urine pH. Code 83986 is for a body-fluid pH assay, not a urinalysis panel.
- 83615LDH testTotal LDH activity$6.04
- Code 83615 measures lactate dehydrogenase, not pH. It may be ordered with pleural-fluid pH, but represents a separate analyte.
83986 billing questions
When should this code be used instead of 83987?
Use 83986 for pH testing of body fluid. Code 83987 is used for exhaled breath condensate.
Does modifier QW apply?
A CLIA-waived version is reported with QW when performed by a site holding a CLIA certificate of waiver.
Is the test paid under the physician fee schedule?
No. Medicare pays 83986 through the CLFS; the test is excluded from the physician fee schedule.
Can pleural-fluid pH be reported with other fluid studies?
Yes. Pleural-fluid pH is commonly evaluated alongside studies such as lactate dehydrogenase, protein, and cell count when clinicians assess an effusion.
Does Medicare payment vary by locality or setting?
No. The CLFS amount is national, with no geographic adjustment or office-versus-facility difference.
Where this amount comes from
FeeBase reads lab amounts directly from the CMS Clinical Laboratory Fee Schedule file for the quarter: one row per code, with its payment indicator and national amount. Contractor-priced tests are labeled, never given a made-up amount. Amounts are Medicare payment limits, not a patient’s bill or a commercial rate.
CMS CLFS 2026 Q4 · effective Oct 1, 2026 through the day before Jan 1, 2027
Show the CMS file line behind this amount
Fee sheets
Put 83986 and the rest of your codes on one sheet
Your codes at your locality, with payer contracts beside Medicare.
Build my fee sheet