Quick answers
- Does Karen Mrejen accept Medicare assignment?
- Yes. Medicare's clinician data says Karen Mrejen 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 Karen Mrejen see?
- In 2024, CMS data shows 493 Original Medicare patients and 2,241 services for Karen Mrejen. This counts Original Medicare only and measures volume, not quality.
- What is Karen Mrejen's NPI number?
- 1902999212. 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 Karen Mrejen, 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 | 493 |
|---|---|
| Services billed to Medicare | 2,241 |
| Different services or procedures | 36 |
| Participating Medicare provider | Yes |
| Average age of these patients | 75 |
Most frequent services
- Visit complexity inherent to evaluation and management associated with medical care services that serve as the continuing focal point for all needed health care services and/or with medical care services that are part of ongoing care related to a patient's (G2211)610 services
- Established patient office or other outpatient visit with low level od decision making, if using time, 20 minutes or more (99213)388 services
- Established patient office or other outpatient visit with moderate level of decision making, if using time, 30 minutes or more (99214)187 services
- Test to measure expiratory airflow and volume (94010)133 services
- Test to examine how well the lungs exchange gases (94729)111 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 pressure75%
- High cholesterol75%
- COPD65%
- Arthritis58%
- Ischemic heart disease54%
- Diabetes37%
Hospitals where Karen Mrejen works
Medicare's Facility Affiliation Data lists Karen Mrejen 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.
- Good Samaritan Hospital Medical CenterWest Islip, NY · Acute Care Hospital · Medicare rating: 3 of 5 stars · Emergency services: listed by Medicare · CCN 330286
- Long Island Jewish Medical CenterNew Hyde Park, NY · Acute Care Hospital · Medicare rating: 4 of 5 stars · Emergency services: listed by Medicare · CCN 330195
- North Shore University HospitalManhasset, NY · Acute Care Hospital · Medicare rating: 5 of 5 stars · Emergency services: listed by Medicare · CCN 330106
- Northwell Hospital Glen CoveGlen Cove, NY · Acute Care Hospital · Medicare rating: 5 of 5 stars · Emergency services: listed by Medicare · CCN 330181
- Ns/Lij HS Southside HospitalBay Shore, NY · Acute Care Hospital · Medicare rating: 3 of 5 stars · Emergency services: listed by Medicare · CCN 330043
Practice locations
Addresses where Karen Mrejen is enrolled with Medicare (CMS data updated October 2, 2026).
- 301 E Main StBay Shore, NY 11706 (631) 986‑3308
- 39 Brentwood RdBay Shore, NY 11706 (631) 666‑5864
Group practices
Medicare enrollment lists Karen Mrejen as a member of this group (CMS data updated October 2, 2026).
- North Shore-Lij Medical PC6,440 clinicians in the group
Specialties
Other pulmonologists in Bay Shore
Clinicians with the same Medicare primary specialty in Bay Shore, NY — not a recommendation.
Other clinicians in North Shore-Lij Medical PC
Medicare enrollment lists these clinicians in the same group practice — not a recommendation.
Clinician information
| Credential | MD |
|---|---|
| Medical school | Albany Medical College Of Union University |
| Graduation year | 1995 (31 years since medical school) |
| Gender (as listed) | Female |
| Medicare assignment | Accepts (Medicare-approved amount as full payment) |
| Telehealth | Offers telehealth services |
| NPI (National Provider Identifier) | 1902999212 |
| 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