Quick answers
- Which hospitals does Mark Mattar work at?
- Medicare's official clinician data lists Mark Mattar at 1 hospital: MedStar Georgetown University Hospital. This is where the clinician works or has privileges; call the hospital to confirm.
- Where does Mark Mattar see patients?
- Medicare's clinician data lists 4 practice locations, including Washington, DC, Leonardtown, MD and Baltimore, MD. Call before your visit to confirm the address.
- What is Mark Mattar's specialty?
- Medicare lists Gastroenterology as the primary specialty, and also Internal Medicine.
- Does Mark Mattar accept Medicare assignment?
- Yes. Medicare's clinician data says Mark Mattar 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 Mark Mattar offer telehealth?
- Medicare's clinician data says Mark Mattar offers telehealth services. Ask the office which visits can be done by video or phone.
- What is the phone number for Mark Mattar?
- (202) 429-2401, as listed in official Medicare / NPI Registry data.
- What is Mark Mattar's NPI number?
- 1841401031. The NPI (National Provider Identifier) is the clinician's permanent federal ID; you can look it up in the official NPI Registry.
Hospitals where Mark Mattar works
Medicare's Facility Affiliation Data lists Mark Mattar at these hospitals (updated 2026-10-02). Each hospital page shows its address, phone, emergency services, Medicare rating and all its clinicians.
- MedStar Georgetown University HospitalWashington, DC · Acute Care Hospital · CCN 090004
Practice locations
Addresses where Mark Mattar is enrolled with Medicare (CMS data updated 2026-10-02).
- 1145 19th St NW, 311 Mmg at 19th Street NWWashington, DC 20036 (202) 429‑2401
- 23511 Hollywood Rd, Suite 2Leonardtown, MD 20650 (301) 997‑0611
- 3800 Reservoir Rd NWWashington, DC 20007
- 4660 Wilkens Ave, Suite 100Baltimore, MD 21229 (410) 247‑0782
Group practices
Medicare enrollment lists Mark Mattar as a member of this group (CMS data updated 2026-10-02).
- MedStar Medical Group II LLC3,767 clinicians in the group
Specialties
- Gastroenterologyprimary
- Internal Medicinealso
Find other Gastroenterology doctors in District of Columbia →
Other gastroenterologists in Washington
Clinicians with the same Medicare primary specialty in Washington, DC — not a recommendation.
Clinician information
| Credential | MD |
|---|---|
| Graduation year | 2004 |
| Gender (as listed) | Male |
| Medicare assignment | Accepts (Medicare-approved amount as full payment) |
| Telehealth | Offers telehealth services |
| NPI (National Provider Identifier) | 1841401031 |
| 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