Quick answers
- Does Gregory T. Havlena accept Medicare assignment?
- Yes. Medicare's clinician data says Gregory T. Havlena accepts Medicare assignment (the Medicare-approved amount as full payment for covered services), as of October 2, 2026. Ask the office to confirm before your visit.
- How many Medicare patients does Gregory T. Havlena see?
- In 2024, CMS data shows 88 Original Medicare patients and 110 services for Gregory T. Havlena. This counts Original Medicare only and measures volume, not quality.
- What is Gregory T. Havlena's NPI number?
- 1598993859. The NPI (National Provider Identifier) is the clinician's permanent federal ID; you can look it up in the official NPI Registry.
Medicare activity in 2024
Official CMS public-use data for Gregory T. Havlena, data year 2024 (released May 21, 2026). It covers Original Medicare (fee-for-service) patients only, not Medicare Advantage or other insurance. It shows volume, not quality or outcomes. CMS hides any count of 10 or fewer patients.
| Original Medicare patients | 88 |
|---|---|
| Services billed to Medicare | 110 |
| Different services or procedures | 37 |
| Participating Medicare provider | Yes |
| Average age of these patients | 66 |
Most frequent services
- Limited ultrasound scan of abdomen (76705)13 services
Chronic conditions among these patients
Share of this clinician’s Original Medicare patients with each condition, as published by CMS (it describes the patients, not the care given).
- High blood pressure66%
- High cholesterol58%
- Diabetes50%
- Chronic kidney disease42%
- Arthritis35%
- Heart failure27%
Hospitals where Gregory T. Havlena works
Medicare's Facility Affiliation Data lists Gregory T. Havlena at these hospitals (updated October 2, 2026). Each hospital page shows its address, phone, emergency services, Medicare rating and all its clinicians. Star rating and emergency services: Hospital General Information (CMS), data updated October 26, 2026.
- Kaiser Foundation Hospital Fontana/OntarioFontana, CA · Acute Care Hospital · Medicare rating: 3 of 5 stars · Emergency services: listed by Medicare · CCN 050140
Practice locations
Addresses where Gregory T. Havlena is enrolled with Medicare (CMS data updated October 2, 2026).
- 2295 S Vineyard AveOntario, CA 91761 (909) 724‑5000
- 9961 Sierra AveFontana, CA 92335 (909) 427‑5000
Group practices
Medicare enrollment lists Gregory T. Havlena as a member of this group (CMS data updated October 2, 2026).
- Southern California Permanente Medical Group11,293 clinicians in the group
Specialties
- Interventional Radiologyprimary
- Diagnostic Radiologyalso
Other interventional radiologists in California
Clinicians with the same Medicare primary specialty in California — not a recommendation.
Other clinicians in Southern California Permanente Medical Group
Medicare enrollment lists these clinicians in the same group practice — not a recommendation.
Clinician information
| Credential | MD |
|---|---|
| Medical school | Johns Hopkins University School Of Medicine |
| Graduation year | 2009 (17 years since medical school) |
| Gender (as listed) | Male |
| Medicare assignment | Accepts (Medicare-approved amount as full payment) |
| NPI (National Provider Identifier) | 1598993859 |
| Corrections | Report an error or suggest an update → |
Most corrections must be made at the source: clinicians update their NPI Registry record (NPPES) and their Medicare enrollment (PECOS); this page follows the next data release.
Sources
- Facility Affiliation Data — Centers for Medicare & Medicaid Services (CMS), data updated October 2, 2026, retrieved October 29, 2026
- Hospital General Information — CMS, data updated October 26, 2026, retrieved November 13, 2026
- National Downloadable File (Doctors and Clinicians) — CMS, data updated October 2, 2026, retrieved October 29, 2026
- Medicare Physician & Other Practitioners - by Provider — CMS, data year 2024, released May 21, 2026; Medicare Physician & Other Practitioners - by Provider and Service
- NPI Registry — U.S. Department of Health and Human Services (NPPES), the clinician’s official record
- Medicare Care Compare — official Medicare tool to look up clinicians