Reena Mahajan, MD
I speak: English
My gender: Female
Where I practice
About me
I am a board-certified medical oncologist and a board-eligible hematologist practicing at Kaiser Permanente’s South Bay Medical Center. I place particular emphasis on emerging therapies and clinical guidelines to ensure members receive up-to-date and effective treatments.
Biography
My path to medicine was shaped by a strong commitment to patient care, research, and community health. I earned my medical degree from the George Washington University School of Medicine in Washington, DC, and completed my internship and residency in internal medicine at Emory University School of Medicine in Atlanta. I went on to serve as an Epidemic Intelligence Service officer with the Centers for Disease Control and Prevention in Atlanta before pursuing fellowship training in hematology and oncology at the UC San Francisco School of Medicine.
These diverse training experiences gave me a broad perspective on oncology and the importance of collaboration in advancing cancer treatment. Over the years, I have been grateful to care for members and their families during some of the most challenging times in their lives, and I consider it a privilege to walk alongside them through their cancer journey.
About my practice
Cancer Subspecialty Focus
My clinical expertise includes the treatment of skin cancers such as melanoma; genitourinary cancers including bladder, kidney, prostate, and testicular cancers; gastrointestinal cancers; breast cancer; lung cancer; thyroid and endocrine tumors; head and neck cancers; thymoma; and both complex malignant and benign hematologic disorders.
Collaboration on Multidisciplinary Teams
I actively participate in regional multidisciplinary tumor boards that bring together experts in medical oncology, radiation oncology, surgery, pathology, and related specialties. These multidisciplinary discussions allow us to deliver coordinated, personalized treatment strategies that reflect the latest standards of care.
Research and Clinical Trials
I am a sub-investigator for the National Cancer Institute (NCI) Community Oncology Research Program (NCORP) and participate in several national clinical trial networks, including SWOG, the National Surgical Adjuvant Breast and Bowel Project (NSABP), NRG Oncology, and the Alliance for Clinical Trials in Oncology. Through these affiliations, I contribute to advancing clinical research and expanding access to leading-edge cancer therapies in the community setting.
How I thrive
Outside of medicine, I enjoy spending time with family and friends, staying active, and making time for activities that keep me balanced. Whether it’s being outdoors, traveling, or pursuing hobbies that bring me joy, I believe that maintaining wellness in my own life helps me better support members in theirs.
My office
Languages spoken by medical staff
Help is available in your language. Learn more.
My provider type
Physicians and SurgeonsMedical groups, plans, and locations
Southern California Permanente Medical Group
Plans accepted
- Exclusive Provider Organization (EPO)
- HMO
- Medi-Cal Managed Care
- Point-of-Service Plan (POS)
- Senior Advantage
Coastline Medical Office
Contact information
- Appointments/Cancellations/Information/Messages
- 1-833-574-2273 (toll free)
My training, certifications and licensing
Medical school
George Washington University School of MedicineBoard certification
Internal Medicine
American Board of Internal MedicineMedical Oncology
American Board of Internal MedicineMedical training
Fellowship
Epidemic Intelligence Service Officer
Centers for Disease Control and PreventionFellowship
Hematology and Oncology
University of California San Francisco School of MedicineInternship
Internal Medicine
Emory University Medical SchoolResidency
Internal Medicine
Emory University Medical SchoolJoined Permanente Medical Group
2023Active license information
License number
A129342License type
Physician and SurgeonLicense issuing state
CALIFORNIANational Provider Identifier (NPI)
1457519910Cultural Competency Training (CCT)
PendingMy hospitals
This information is not available at this time.
To find a provider's office hours, search our facility directory.
The information in this online directory is updated periodically. The availability of physicians, hospitals, providers, and services may change. Information about a practitioner is provided to us by the practitioner or is obtained as part of the credentialing process. If you have questions, please call us at 1-800-464-4000 (toll free). For the hearing and speech impaired: 1-800-464-4000 (toll free) or TTY 711 (toll free). You can also call the Medical Board of California at 916-263-2382, or visit their website.
We want to speak to you in the language that you’re most comfortable with when you call or visit us. Qualified interpreter services, including sign language, are available at no cost, 24 hours a day, 7 days a week during all hours of operations at all points of contact. We do not encourage the use of family, friends or minors as interpreters. Only the services of interpreters and qualified staff are used to provide language assistance. These may include bilingual providers, staff, and healthcare interpreters. In-person, telephone, video, and alternative modes of communication are available. Learn more about interpreter services.
If you would like to report an error in provider or facility information, please contact us.
Medicare Members: To request a hard copy of Kaiser Permanente’s provider directory, please call our Member Services department at 1-800-443-0815, seven days a week, 8 a.m. to 8 p.m. Kaiser Permanente will mail a hard copy of the provider directory to you within three (3) business days of your request. Kaiser Permanente may ask whether your request for a hard copy is a one-time request or if you are requesting to receive the provider directory in hard copy permanently.
If you request it, your request for hard copies of the provider directory remains until you leave Kaiser Permanente or request that hard copies be discontinued.
Medi-Cal Members: This directory includes Kaiser Permanente’s outpatient pharmacies. You can get any drugs covered by Kaiser Permanente at one of these pharmacies. You can get outpatient drugs covered by Medi-Cal at any Medi-Cal Rx Pharmacy. It does not have to be a Kaiser Permanente network pharmacy. Most Kaiser Permanente network pharmacies are Medi-Cal Rx pharmacies. Your pharmacy can tell you if it is part of the Medi-Cal Rx network. If you want to find a Medi-Cal pharmacy outside of Kaiser Permanente, you can use the Medi-Cal Rx Pharmacy Locator online at www.Medi-CalRx.dhcs.ca.gov. You can also call Medi-Cal Rx Customer Service at 1-800-977-2273, 24 hours a day, 7 days a week (TTY 711 Monday through Friday, 8 a.m. to 5 p.m.).
Medi-Cal Members: Enhanced Care Management and Community Supports services require prior authorization and are limited to members who meet specific eligibility criteria.
Kaiser Permanente enrollees have full and equal access to covered services, including enrollees with disabilities as required under the Federal Americans with Disabilities Act of 1990 and Section 504 of the Rehabilitation Act of 1973.
Kaiser Permanente uses the same quality, member experience, or cost-related measures to select practitioners and facilities in Marketplace Silver-tier plans as it does for all other Kaiser Foundation Health Plan (KFHP) products and lines of business. The measures may include, but are not limited to, HEDIS/CAHPS performance, member/patient complaints, patient safety scores, hospital quality measures, and geographic need. Members enrolled in KFHP Marketplace plans have access to all professional, institutional and ancillary health care providers who participate in KFHP plans’ contracted provider network, in accordance with the terms of members’ KFHP plan of coverage. All Kaiser Permanente Medical Group physicians and network physicians are subject to the same quality review processes and certifications.
Kaiser Permanente uses the same geographic distribution consideration to select hospitals in Marketplace plans as it does for all other Kaiser Foundation Health Plan (KFHP) products and lines of business. Accessibility of medical offices and medical centers in this directory: All Kaiser Permanente facilities are accessible to members.
This page was last updated on: 12/03/2025