Dr. Patrick S Chang , MD
Internal Medicine โข Mather, CA
10535 Hospital Way
Mather, CA 956554200
This profile restates public CMS/NPPES data; T-MedInfo gives no medical advice — consult a licensed professional, and call 911 for emergencies.
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Dr. Patrick Chang is listed in NPPES under Internal Medicine.
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NPI assigned on February 23, 2006; this date does not establish years in practice.
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Published CMS data list 586 Original Medicare Part B services in 2019.
Source: CMS, Medicare Physician & Other Practitioners โ by Provider and Service, 2019. Published rows only; this is not a quality measure.
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Published Part B service records, 2019:
- 99214 โ Established patient outpatient office visit: 449 service units.
- J3420 โ Injection, vitamin b-12 cyanocobalamin, up to 1000 mcg: 85 service units.
- 99211 โ outpatient office visit: 21 service units.
Source: CMS, Medicare Physician & Other Practitioners โ by Provider and Service, 2019. Units differ by code; these are not visits or a measure of quality.
CPTยฎ only copyright 2018 American Medical Association. All rights reserved. Service names are shortened from CPT Consumer Friendly Descriptors (CMS data, 2019). CPT notice
See all 5 records in the table ยท Guide: How to read Medicare Part B data
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Published CMS data list 1,352 Medicare Part D prescriptions, including refills, in 2019.
Source: CMS, Medicare Part D Prescribers โ by Provider and Drug, 2019. Published rows only; this is not a quality measure.
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Published Part D records, 2019:
- Levothyroxine Sodium โ 127 prescription fills, including refills.
- Atorvastatin Calcium โ 88 prescription fills, including refills.
- Metformin Hcl โ 88 prescription fills, including refills.
Source: CMS, Medicare Part D Prescribers โ by Provider and Drug, 2019. Drug names come from pharmacy claims. Listing a drug here is not an endorsement or a recommendation.
See all 42 records in the table ยท Guide: How to read Medicare Part D prescriber data
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Medicare Part B services went from 12,516 in 2017 to 586 in 2019.
Source: CMS, Medicare Physician & Other Practitioners โ by Provider and Service, 2017โ2019.
Practice Location & Contact Primary Location
10535 Hospital Way
Mather, CA 956554200
Matched by practice address or phone in NPPES. A shared address or phone does not confirm that this clinician works there.
What Public CMS Data Show
Internal Medicine: NPPES taxonomy is a reported classification, not proof of board certification.
Medicare patients
237 people with Original Medicare in 2019
It gives a sense of how many people with Medicare this clinician treated that year.
Source: CMS, Medicare Physician & Other Practitioners โ by Provider, 2019.
Medicare-allowed amount
About $52,029 in 2019
The total amount Medicare approved for these services in 2019. It includes what Medicare paid and what patients or their other insurance owed, such as the deductible and coinsurance.
It shows the total cost of this clinician's Original Medicare services under Medicare's fee rules.
What this does not show: Medicare-allowed amount
This is not the clinician's income. Part of it can go to a clinic or group practice, staff, equipment or drugs. It is not the price you will pay.
Source: CMS, Medicare Physician & Other Practitioners โ by Provider and Service, 2019.
Paid by Medicare
About $24,155 in 2019
The part of the Medicare-allowed amount that Medicare itself paid in 2019, after patients' deductibles and coinsurance.
The gap between the allowed amount and this number is roughly what patients and their other insurance paid.
What this does not show: Paid by Medicare
This is not the clinician's income and not a measure of quality.
Source: CMS, Medicare Physician & Other Practitioners โ by Provider and Service, 2019.
30-day fills
3,478 standardized 30-day fills in 2019
CMS converts prescriptions to 30-day supplies so they can be compared. A 90-day prescription counts as about three 30-day fills.
What this does not show: 30-day fills
It is not a count of patients and not a measure of quality.
Part D drug cost
$29,497 in 2019
The total cost of these prescriptions in 2019, paid by Medicare drug plans, patients and other payers together.
It shows the total spending on drugs this clinician prescribed, not what any one patient paid.
What this does not show: Part D drug cost
A higher cost often reflects the type of medicines a specialty uses. It is not your out-of-pocket cost and not a measure of quality.
Source: CMS, Medicare Part D Prescribers โ by Provider and Drug, 2019.
Industry payments (Open Payments)
Fewer than 11 payment records totaling $13.89 in 2022
Drug and medical device companies must report certain payments to doctors and some other clinicians to CMS, such as meals, travel, speaking fees or research funding.
It shows reported financial ties between this clinician and companies. You can ask your clinician about them.
These records are submitted by drug and medical device companies, and a reported payment does not necessarily mean the financial relationship is improper.
General: payments not tied to research, such as meals, travel, consulting or speaking fees.
A reported payment does not necessarily mean the financial relationship is improper. Research payments can go to a hospital or university for a study the clinician leads, not to the clinician personally. Clinicians can dispute records with the company that reported them.
Source: CMS Open Payments, program year 2022.
NPI first issued
2006
The year this clinician's National Provider Identifier (NPI) was issued. An NPI is a unique 10-digit ID that US health care providers use for billing.
What this does not show: NPI first issued
NPIs have been issued only since 2005, so this year is not necessarily when the clinician started practicing.
Source: CMS NPPES NPI Registry.
Medicare assignment not listed
CMS data do not show whether this clinician accepts Medicare assignment. This does not mean they do not accept Medicare. Ask the office.
Medicare assignment applies to Original Medicare. It does not tell you whether the clinician is in a Medicare Advantage plan's network, accepts other insurance, or is taking new patients.
Source: CMS Doctors and Clinicians, CMS release of October 2, 2026; Medicare.gov, โDoes your provider accept Medicare as full payment?โ
No telehealth indicator
CMS shows this indicator only when recent Medicare claims include telehealth services. The clinician may still offer telehealth; ask the office.
Source: CMS, Telehealth Indicator on Medicare Care Compare (fact sheet, January 2023); CMS Doctors and Clinicians, CMS release of October 2, 2026.
Enrolled in Medicare (PECOS)
Dr. Chang has a Medicare enrollment record in PECOS, the CMS system clinicians use to enroll so they can bill Medicare or order services for people with Medicare.
It does not show whether the clinician accepts assignment, is in your plan's network, or is taking new patients.
Source: CMS Medicare Fee-For-Service Public Provider Enrollment (PECOS); CMS Order and Referring file.
Can order Medicare-covered services
CMS lists Dr. Chang as eligible to order or refer Medicare Part B clinical laboratory and imaging services, durable medical equipment (DME) and home health services for people with Medicare.
Medicare pays for these items and services only when they are ordered by an eligible clinician.
What this does not show: Can order Medicare-covered services
It does not mean the clinician offers these services directly.
Source: CMS Medicare Fee-For-Service Public Provider Enrollment (PECOS); CMS Order and Referring file.
Compared with the same specialty in Mather and California
Billing and prescribing volume is not a quality rating.
Medicare Part B
Comparisons use 2024 data. The latest CMS data for Dr. Chang are from 2019.
Medicare Part D
Comparisons use 2024 data. The latest CMS data for Dr. Chang are from 2019.
26 active clinicians are listed under Internal Medicine with a practice address in Mather, CA (17,897 in California).
Addresses are self-reported to NPPES and may be out of date.
Telehealth indicator in Mather
0% of these 26 clinicians have the CMS telehealth indicator.
15.4% of these 26 clinicians are listed by CMS as accepting Medicare assignment.
CMS data by year
Changes may reflect reporting, coverage or privacy limits, not changes in care quality.
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Medicare Part B services
Medicare Part B services decreased 95% from 12,516 in 2017 to 586 in 2019.
- 2017: 12,516
- 2018: 6,966
- 2019: 586
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Medicare-allowed amount
Medicare-allowed amount decreased 94% from $843,164 in 2017 to $52,029 in 2019.
- 2017: $843,164
- 2018: $456,618
- 2019: $52,029
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Paid by Medicare
Paid by Medicare decreased 96% from $659,490 in 2017 to $24,155 in 2019.
- 2017: $659,490
- 2018: $339,121
- 2019: $24,155
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Medicare Part D prescriptions
Medicare Part D prescriptions decreased 75% from 5,314 in 2015 to 1,352 in 2019.
- 2015: 5,314
- 2016: 5,770
- 2017: 6,040
- 2018: 4,689
- 2019: 1,352
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30-day fills
30-day fills decreased 69% from 11,188 in 2015 to 3,478 in 2019.
- 2015: 11,188
- 2016: 12,492
- 2017: 13,346
- 2018: 10,944
- 2019: 3,478
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Part D drug cost
Part D drug cost decreased 93% from $398,839 in 2015 to $29,497 in 2019.
- 2015: $398,839
- 2016: $379,368
- 2017: $362,374
- 2018: $284,824
- 2019: $29,497
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Industry payments (Open Payments)
CMS data for industry payments (Open Payments) are available for 2022 only.
Sources: CMS Medicare Physician & Other Practitioners (2019), CMS Medicare Part D Prescribers (2019), CMS Open Payments (2022), CMS Doctors and Clinicians, CMS release of October 2, 2026, CMS NPPES NPI Registry. Specialty names follow the NUCC Health Care Provider Taxonomy.
Text: T-MedInfo ยท Report an error.
Pharma & Medical Device Financial Disclosures
Payments and other transfers of value that drug and medical device companies reported to CMS Open Payments
Program year 2022 (payments made January 1 โ December 31, 2022): fewer than 11 records totaling $13.89.
| Manufacturer | Payment Nature | Product | Type | Amount ($) |
|---|---|---|---|---|
| ABBVIE INC. |
Food and Beverage
In-kind items and services
|
VRAYLAR | General | $13.89 |
Source: CMS Open Payments, program year 2022, released June 30, 2026.
Performed Procedures & Service Volume
CPTยฎ is a registered trademark of the American Medical Association. CPT codes, descriptions and other data only are copyright 2016โ2018 American Medical Association. All rights reserved. Applicable FARS/HHSARS apply. Descriptions of CPT codes are the AMA's CPT Consumer Friendly Descriptors as published by CMS in the Medicare Physician & Other Practitioners โ by Provider and Service data, 2017โ2019; they are plain-language summaries, not for clinical coding or documentation. HCPCS Level II codes and descriptions are from CMS. Fee schedules, relative value units, conversion factors and/or related components are not assigned by the AMA, are not part of CPT, and the AMA is not recommending their use. The AMA does not directly or indirectly practice medicine or dispense medical services. The AMA assumes no liability for data contained or not contained herein.
| HCPCS Code | Services | Patients | Submitted Charge | Medicare Allowed |
|---|---|---|---|---|
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99214
Established patient office or other outpatient visit with moderate level of decision making, if using time, 30 minutes or more
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449 | 232 | $136.44 | $107.31 |
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J3420
Injection, vitamin b-12 cyanocobalamin, up to 1000 mcg
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85 | 45 | $5.05 | $1.72 |
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99211
Office or other outpatient visit for the evaluation and management of established patient that may not require presence of healthcare professional
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21 | 19 | $30.33 | $22.31 |
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93882
Ultrasound of one side of head and neck blood flow
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16 | 16 | $258.00 | $113.28 |
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93979
Ultrasound of aorta, vena cava, groin vessels or bypass grafts
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15 | 15 | $150.00 | $94.63 |
Source: CMS Part B by Provider and Service, 2019; services under 11 beneficiaries omitted by CMS. Privacy limits
Submitted charges are billed amounts, not a price quote for your visit.
Medicare Part D Prescribing Profile & Medications
Medicare Part D prescriptions filled, including refills, in 2019.
| Brand Name | Generic Name | Prescriptions | Day Supply | Total Cost | Patients |
|---|---|---|---|---|---|
| Levothyroxine Sodium | Levothyroxine Sodium | 127 | 10,553 | $2,931.87 | 61 |
| Atorvastatin Calcium | Atorvastatin Calcium | 88 | 7,050 | $1,618.67 | 42 |
| Metformin Hcl | Metformin Hcl | 88 | 7,134 | $794.00 | 41 |
| Lisinopril | Lisinopril | 84 | 6,770 | $670.50 | 38 |
| Simvastatin | Simvastatin | 83 | 7,050 | $901.70 | 38 |
| Montelukast Sodium | Montelukast Sodium | 74 | 4,980 | $1,566.22 | 28 |
| Amlodipine Besylate | Amlodipine Besylate | 63 | 5,310 | $483.58 | 28 |
| Atenolol | Atenolol | 54 | 4,250 | $608.90 | 18 |
| Omeprazole | Omeprazole | 46 | 3,585 | $668.92 | 21 |
| Gabapentin | Gabapentin | 43 | 3,390 | $1,029.66 | 20 |
| Tamsulosin Hcl | Tamsulosin Hcl | 37 | 3,090 | $1,082.45 | 16 |
| Metoprolol Succinate | Metoprolol Succinate | 32 | 2,574 | $1,619.09 | 21 |
| Losartan Potassium | Losartan Potassium | 30 | 2,085 | $395.98 | 13 |
| Trazodone Hcl | Trazodone Hcl | 29 | 1,548 | $336.87 | 15 |
| Allopurinol | Allopurinol | 25 | 2,190 | $585.04 | 15 |
| Terazosin Hcl | Terazosin Hcl | 24 | 2,160 | $876.29 | โ |
| Rosuvastatin Calcium | Rosuvastatin Calcium | 24 | 2,094 | $1,064.98 | 14 |
| Lovastatin | Lovastatin | 23 | 1,884 | $528.56 | 11 |
| Furosemide | Furosemide | 22 | 1,380 | $84.68 | โ |
| Hydrochlorothiazide | Hydrochlorothiazide | 22 | 1,980 | $238.28 | 11 |
| Pantoprazole Sodium | Pantoprazole Sodium | 22 | 1,860 | $661.73 | 12 |
| Pravastatin Sodium | Pravastatin Sodium | 21 | 1,546 | $371.19 | โ |
| Methylprednisolone | Methylprednisolone | 19 | 114 | $241.78 | 18 |
| Fenofibrate | Fenofibrate | 19 | 1,710 | $1,427.28 | โ |
| Ezetimibe | Ezetimibe | 19 | 1,710 | $1,364.46 | โ |
(top 25 shown)
Source: CMS Part D by Provider and Drug, 2019; rows below 11 claims omitted by CMS; volume isn’t quality. Privacy limits
Specialties & License Numbers Reported to NPPES
Self-certified to NPPES: 2025-12-26NUCC Taxonomy Code: 207R00000X
A physician who provides long-term, comprehensive care in the office and the hospital, managing both common and complex illness of adolescents, adults and the elderly. Internists are trained in the diagnosis and treatment of cancer, infections and diseases affecting the heart, blood, kidneys, joints and digestive, respiratory and vascular systems. They are also trained in the essentials of primary care internal medicine, which incorporates an understanding of disease prevention, wellness, substance abuse, mental health and effective treatment of common problems of the eyes, ears, skin, nervous system and reproductive organs.
Additional State Medicaid & Healthcare Payer Identifiers
Medicare (PECOS) Enrollment & Ordering Eligibility
Source: CMS PECOSORDER AND REFERRING ONLY - INTERNAL MEDICINE
I20260127003574
AZ
8022078534
Sources: CMS Provider Enrollment and Order and Referring. Medicare enrollment is a billing status, not an accreditation or quality rating.
Clinicians Sharing This Practice Address or Phone
Clinicians sharing this NPPES address, phone or fax; a shared contact does not mean they work together.
Family Medicine
Doctor of Osteopathic Medicine (D.O.)
Psychiatry & Neurology - Psychiatry
Pathology - Clinical Pathology
Doctor of Medicine (M.D.)
Emergency Medicine
Doctor of Medicine (M.D.)
Nurse Practitioner - Family
Advanced Registered Nurse Practitioner
Family Medicine
Doctor of Medicine (M.D.)
Career & Practice History Timeline
Changes recorded in monthly NPPES data files: addresses, names, credentials, specialties and NPI status
Registered at 10535 HOSPITAL WAY, MATHER, CA 956554200 (Tel: 9168437000)
Registered at 10535 HOSPITAL WAY, MATHER, CA 956554200 (Tel: 9168437000)
NPI status registered as active in NPPES database
Registered at 600 S DOBSON RD, STE E39, CHANDLER, AZ 852245678 (Tel: 4807775888)
Registered at 600 S DOBSON RD, STE E39, CHANDLER, AZ 852245693 (Tel: 4807775888)
Recorded as PATRICK CHANG, MD
Internal Medicine (license number reported to NPPES: AZ 21908)
First registered as active Individual Practitioner in NPPES Database.
NPI Administrative Meta
Other Internal Medicine Providers in Mather
Mailing Address
10535 Hospital Way
Mather, CA 956554200
Phone: 9168437000