California Medicaid overpaid $13.9M for lab tests, OIG finds
Summary
A federal audit of California's Medicaid program found the state paid providers more than Medicare-linked limits allow for clinical lab tests -- bloodwork and other diagnostic services -- on 70% of the 3.1 million claims it reviewed in detail. The report doesn't allege fraud; it traces the overpayments to a rate table California's own health agency didn't keep current, by its own account. The confirmed tab is $13.9 million, with a further $29.3 million still unresolved -- and part of that remainder is money California disputes owing at all.
A $632 million universe, narrowed down
's audit covered $632.2 million in Medicaid lab-test payments for 36.3 million services claimed by California's Department of Health Care Services (DHCS). Within that, auditors identified $187.5 million in payments across 11.3 million services that potentially exceeded Medicare's fee schedule. Given the volume, limited its detailed line-by-line review to a subset of $107.5 million covering 3.1 million services -- and it's that reviewed subset the audit's headline findings are drawn from.
View data as table
| Paid above the allowed limit | 2,186,277 |
|---|---|
| Paid within the allowed limit | 726,165 |
| Potentially overpaid (ambiguous) | 211,171 |
Seven in ten reviewed claims were overpaid
Of the 3.1 million services reviewed closely, 2,186,277 -- 70% -- were paid more than Medicare or California's own rules allow. Only 726,165 were within limits. A further 211,171 services, tied to prenatal-screening lab tests, potentially exceeded the allowed amount too, but couldn't fully confirm those because they were billed and paid before a state rate increase for those specific tests had taken effect -- a genuine timing ambiguity, not a clear-cut overpayment.
View data as table
| Potential additional overpayment (unresolved) | 29,319,373 |
|---|---|
| Confirmed overpayment | 13,892,037 |
The cause: a rate table nobody updated
The overpayments trace to one specific breakdown: DHCS didn't follow its own procedures for reviewing and updating laboratory reimbursement rates in its claims-processing system, so payments stayed above the Medicare-linked ceiling as that ceiling changed. The state agency told the lapse came down to a clerical error -- not a policy decision, and not concealment. As a result, the federal reimbursement California claimed exceeded allowed rates by $13,892,037, and potentially exceeded them by a further $29,319,373 still pending resolution with .
A rate that swung from nearly all-overpaid to none, and back
The year-by-year data complicates a simple 'one clerical slip' story. In 2019, 99.9% of reviewed services were overpaid -- essentially every claim checked. That collapsed to 7.6% in 2020, suggesting the rate table was corrected around then. But the overpayment rate climbed right back afterward: 62.2% in 2021, 83.9% in 2022, and 100% in 2023 -- every single reviewed 2023 service exceeded the allowed limit. Whatever got fixed after 2019 either broke again or was overtaken by subsequent Medicare rate changes the state didn't track.
View data as table
| 2019 | 99.9% | 321,954 of 322,204 reviewed services |
|---|---|---|
| 2020 | 7.6% | 42,120 of 550,761 reviewed services |
| 2021 | 62.2% | 526,132 of 846,230 reviewed services |
| 2022 | 83.9% | 566,569 of 674,916 reviewed services |
| 2023 | 100% | 729,502 of 729,502 reviewed services |
Four recommendations -- and one California disputes
recommended DHCS refund $7,576,103 -- the federal share of the confirmed overpayment -- to Washington; work with to determine how much of the $16,477,416 potential federal share is owed; review payments made since the audit period for further overpayments and refund those too; and strengthen its rate-review procedures going forward. DHCS formally concurred with all four, and said it is already reviewing and standardizing the policies governing how it maintains its reimbursement rate tables.
But 'concurred' undersells what DHCS actually argues about the largest piece of the potential $16.5 million: that money covers prenatal genetic-screening tests DHCS says are billed as preventive care under a different Medi-Cal benefit category entirely, not subject to the clinical-lab rate limits at issue -- a position DHCS says two 2022-2023 -approved rate amendments support. DHCS agreed to the recommended process (confirm the answer with ) without agreeing the money is actually owed. OIG's own report⧉ notes that a prior data analysis flagged multiple states, including California, as at risk of similar noncompliance, and that this audit is part of a broader multi-state series -- though the report doesn't name the other states or say where their reviews stand.
The takeaway
- Seven in ten reviewed claims were overpaid, and the confirmed cause was mundane -- but it didn't stay fixed. $13.9 million in confirmed overpayment traces to a rate table California's own health agency didn't keep current. The overpayment rate fell sharply after 2019, then climbed back to 100% by 2023, suggesting more than a single missed update.
- The number could grow, and part of it is actively disputed. A further $29.3 million in potential overpayments remains unresolved, and wants California to keep checking payments made since the audit period. But roughly $16.5 million of that unresolved total is money DHCS argues isn't an overpayment at all, because it says those specific tests fall outside the benefit category the rate limit applies to.
- California agreed to follow every recommended process, without agreeing every dollar is owed. DHCS is changing its rate-review procedures and accepted the $7.6 million confirmed refund, but formally concurring with a recommendation to 'work with to determine' an amount is not the same as agreeing that amount is owed -- a distinction the audit's own numbers don't resolve.
's audit does not allege fraud or intentional misconduct by California or by lab providers. 's own finding is procedural -- DHCS did not follow its rate-update procedures -- and the 'clerical error' characterization in this piece is DHCS's own explanation, given in its written response in the report's Appendix B, not an independent finding, though 's findings don't contradict it. The $29.3 million 'potential' figure is explicitly unresolved in the report itself: $16.5 million of it covers prenatal-screening tests DHCS disputes were overpaid at all, and the remainder involves a rate-change timing ambiguity could not resolve on its own. No refund timeline beyond DHCS's written commitment is stated in the report, and the report does not indicate whether the $7.6 million confirmed refund has yet been paid.
Sources(2) ▾
- U.S. Department of Health and Human Services, Office of Inspector General, California Claimed at Least $13.9 Million More in Medicaid Reimbursements for Clinical Diagnostic Laboratory Services Than Was Allowed by Federal and State Requirements (OAS-25-01-076) (2026-06-01) — The full - audit report, read directly for this piece via its extractable text layer (no needed). Covers California's fee-for-service Medicaid payments for clinical diagnostic laboratory services during calendar years 2019-2023, and includes the full text of the State agency's written response in Appendix B. oig.hhs.gov · original document
- U.S. Department of Health and Human Services, Office of Inspector General, OAS-25-01-076 Highlights (2026-06-01) — 's own two-page summary of the same audit, used to cross-check the headline figures and recommendation language against the full report. oig.hhs.gov · original document
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Medicaid reimbursement for clinical diagnostic laboratory tests -- bloodwork and other diagnostic services -- generally cannot exceed what Medicare would pay for the same test. A June 2026 HHS Office of Inspector General audit⧉ examined California's fee-for-service Medicaid payments for these tests from 2019 through 2023, and found the state had been claiming federal reimbursement above that limit. The report doesn't allege fraud; traces the root cause to a procedural failure -- the state's own health agency didn't keep a reimbursement rate table current -- which the agency itself attributed to a clerical error.