Quick answers
- Which hospitals does John M. Wallmark work at?
- Medicare's official clinician data lists John M. Wallmark at 4 hospitals: Adventist Healthcare Shady Grove Medical Center, Holy Cross Germantown Hospital, Sibley Memorial Hospital and Suburban Hospital. This is where the clinician works or has privileges; call the hospital to confirm.
- Where does John M. Wallmark see patients?
- Medicare's clinician data lists 5 practice locations, including Columbia, MD, Silver Spring, MD and Bethesda, MD. Call before your visit to confirm the address.
- What is John M. Wallmark's specialty?
- Medicare lists Hematology/Oncology as the primary specialty.
- Does John M. Wallmark accept Medicare assignment?
- Yes. Medicare's clinician data says John M. Wallmark accepts Medicare assignment (the Medicare-approved amount as full payment for covered services), as of 2026-10-02. Ask the office to confirm before your visit.
- Does John M. Wallmark offer telehealth?
- Medicare's clinician data says John M. Wallmark offers telehealth services. Ask the office which visits can be done by video or phone.
- What is the phone number for John M. Wallmark?
- (410) 964-2218, as listed in official Medicare / NPI Registry data.
- What is John M. Wallmark's NPI number?
- 1689755365. The NPI (National Provider Identifier) is the clinician's permanent federal ID; you can look it up in the official NPI Registry.
Hospitals where John M. Wallmark works
Medicare's Facility Affiliation Data lists John M. Wallmark at these hospitals (updated 2026-10-02). Each hospital page shows its address, phone, emergency services, Medicare rating and all its clinicians.
- Adventist Healthcare Shady Grove Medical CenterRockville, MD · Acute Care Hospital · CCN 210057
- Holy Cross Germantown HospitalGermantown, MD · Acute Care Hospital · CCN 210065
- Sibley Memorial HospitalWashington, DC · Acute Care Hospital · CCN 090005
- Suburban HospitalBethesda, MD · Acute Care Hospital · CCN 210022
Practice locations
Addresses where John M. Wallmark is enrolled with Medicare (CMS data updated 2026-10-02).
- 10710 Charter Dr, Suite G020Columbia, MD 21044 (410) 964‑2218
- 11886 Healing WaySilver Spring, MD 20904 (301) 933‑3216
- 6420 Rockledge Dr, Suite 4200Bethesda, MD 20817 (301) 929‑0765
- 7350 Van Dusen Rd, Suite 370Laurel, MD 20707 (301) 982‑9800
- 9905 Medical Ctr DrRockville, MD 20850
Group practices
Medicare enrollment lists John M. Wallmark as a member of this group (CMS data updated 2026-10-02).
- Maryland Oncology Hematology PA104 clinicians in the group
Specialties
- Hematology/Oncologyprimary
Other hematologist-oncologists in Columbia
Clinicians with the same Medicare primary specialty in Columbia, MD — not a recommendation.
Clinician information
| Credential | MD |
|---|---|
| Medical school | Hahnemann University College Of Medicine |
| Graduation year | 1992 |
| Gender (as listed) | Male |
| Medicare assignment | Accepts (Medicare-approved amount as full payment) |
| Telehealth | Offers telehealth services |
| NPI (National Provider Identifier) | 1689755365 |
| 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 2026-10-02, retrieved 2026-10-29
- National Downloadable File (Doctors and Clinicians) — CMS, data updated 2026-10-02, retrieved 2026-10-29
- 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