Dr. Warren David Johnston, MD

Dr. Johnston practices at Providence St. Joseph Hospital Orange in Orange, California, part of Providence Health & Services.

Dr. Johnston's NPI, 1427052802, was assigned on June 13, 2005. Dr. Johnston graduated from University of Rochester Medical Center in 1975. Dr. Johnston holds California license G33255.

Dr. Johnston's primary practice is Providence St. Joseph Hospital Orange, at 1100 West Stewart Dr, Orange, CA 92868 in Orange County. The practice phone is (714) 633-9111.

Dr. Johnston's primary practice is Providence St. Joseph Hospital Orange in Orange, California, part of Providence Health & Services. The medical group on file is St. Jude Heritage Medical Group. Dmand AI also links Dr. Johnston to 1 more group practice or clinic, named with a free account.

Dmand AI tracks the electronic health record (EHR) system at each site where Dr. Johnston practices, 2 sites in all. Vendor and product names are available with a free account.

Cardiovascular disease is Dr. Johnston's primary specialty in the NPI Registry, under taxonomy code 207RC0000X. Dr. Johnston is board certified in cardiovascular disease by the American Board of Internal Medicine. Dr. Johnston is licensed in California.

Dmand AI lists aneurysm, aortic atherosclerois, arterial blot clot /embolism, atrial fibrillation and flutter, cardiomyopathy, cerebrovascular disease, chronic hypertension and chronic skin ulcer among the conditions Dr. Johnston treats.

CMS data shows 1,223 Medicare services from Dr. Johnston across 10 procedure codes in 2024, for 538 Medicare patients. Medicare paid $110,028 for them.

CMS counts 538 Medicare patients who saw Dr. Johnston in 2024. The largest group is 65 to 74, with 221 patients. 75% of them have high blood pressure, and 75% have high cholesterol. 14% are also on Medicaid. Their average risk score is 1.99, where 1.00 is the Medicare average, so they are sicker than most Medicare patients.

Across all payers, Dmand AI patient panel data puts Dr. Johnston's median patient age at 71, with 54% women.

In 2024, Dr. Johnston wrote 5,505 Medicare Part D claims for 897 patients. 84% of them were for generic drugs. CMS names the drug for 5,260 of them, across 49 drugs with 11 or more claims each, at $996,695 in total drug cost. In 2023, CMS named 4,869 claims across 47 drugs.

Dr. Johnston accepts Medicare assignment, so Medicare's approved amount is taken as full payment. CMS lists Dr. Johnston as offering telehealth.

Dmand AI links 2 papers to Dr. Johnston in 2025. Dr. Johnston's most frequent co-authors are Byron J J. Allen, MD, Mehrdad Kevin Ariani and Peng-Sheng Chen, MD.

CMS Open Payments shows 215 general payments to Dr. Johnston from 28 drug and device companies from 2016 to 2025. Food and beverage make up the largest share, 100% of the total. Abbott Laboratories paid the most, $1,264.

Dmand AI lists 3 awards for Dr. Johnston, most recently ACP Fellow in 2012.

Dr. Johnston graduated from University of Rochester Medical Center in 1975. Dr. Johnston is a member of ACC, ACP and AHA.

Dr. Johnston is in network with 13 carriers, including Aetna, Elevance and Blue Cross Blue Shield of Michigan. PPO plans come from the most carriers, 9. Check the plan with the practice before a visit.