About
Collin D. Cullen, MD brings a lifetime of roots in Washington, DC to his concierge internal medicine practice. He earned a Bachelor of Arts in Biology and English from LaSalle University in 1989, then went on to Georgetown University School of Medicine, where he received his Doctorate of Medicine in 1993. He completed both his internship and internal medicine residency at Geisinger Medical Center in Danville, Pennsylvania, finishing as Chief Resident in Internal Medicine and Pediatrics in 1997. The American Board of Internal Medicine has board-certified Dr. Cullen, and he holds licenses in both Maryland and the District of Columbia.
Dr. Cullen has practiced primary care alongside his brothers for 21 years, building on a family tradition his father established over a 30-year career as a DC-area general practitioner. He serves patients through an MDVIP-affiliated practice that centers the doctor-patient relationship above all else. He believes that listening to the patient remains the most important diagnostic tool a physician has. Sibley Memorial Hospital holds his hospital affiliation, and he serves on the hospital's Department of Medicine as Secretary and Treasurer. Washingtonian Magazine has named him a Top Doctor every year since 2000, and Castle Connolly recognized him as a Top Doctor from 2019 through 2024.
Education & Training
Undergraduate
LaSalle University, Philadelphia, PA — Bachelor of Arts, Biology and English 1989
Medical School
Georgetown University School of Medicine, Washington, DC — Doctorate of Medicine 1993
Residency
Internal Medicine, Geisinger Medical Center, Danville, PA 1994-1997; Chief Resident, Internal Medicine & Pediatrics 1997
Additional Training
Internship: Geisinger Medical Center, Danville, PA 1993-1994
Certifications
Who is Dr. Cullen right for?
Dr. Cullen is well-suited for adults in Northwest DC and Montgomery County, Maryland who want a long-term relationship with a single physician. Patients focused on preventive care and chronic disease management benefit from his background in internal medicine. His 24/7 availability by phone makes him a strong fit for those who want reliable after-hours access. Adults who value a physician with deep community knowledge and multigenerational medical roots will find his practice especially familiar.
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Frequently Asked Questions
Dr. Cullen specializes in internal medicine and preventive medicine. He emphasizes comprehensive screenings, custom wellness planning, and proactive management of chronic conditions. His approach prioritizes the doctor-patient relationship as the foundation of effective care.
Yes, Dr. Cullen holds board certification from the American Board of Internal Medicine. He completed his residency training at Geisinger Medical Center and served as Chief Resident in Internal Medicine and Pediatrics in 1997.
Dr. Cullen earned his medical degree from Georgetown University School of Medicine in Washington, DC. He completed his internship and internal medicine residency at Geisinger Medical Center in Danville, Pennsylvania, finishing as Chief Resident in 1997.
Dr. Cullen has practiced primary care in the Washington, DC area throughout his entire professional career, spanning over 21 years. He has deep roots in the community, having grown up in the DC area where his father practiced as a general practitioner for 30 years.
Dr. Cullen holds an affiliation with Sibley Memorial Hospital in Washington, DC. He serves on the Department of Medicine as Secretary and Treasurer and has participated in peer review since 2015.
Washingtonian Magazine has honored Dr. Cullen with its Top Doctor Award every year since 2000. Castle Connolly also named him a Top Doctor from 2019 through 2024. These recognitions reflect his long-standing reputation in the Northwest DC and Montgomery County communities.
Dr. Cullen believes the doctor-patient connection forms the foundation of successful healthcare. He considers listening to the patient the most important diagnostic tool available. His practice prioritizes prevention, and he builds long-term relationships with each of his members.
Yes, Dr. Cullen offers same- or next-day appointments that start on time. His smaller panel size through the MDVIP network allows him to accommodate urgent needs quickly without long waits.
Doctor profile last updated April 10, 2026