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MERCEDES M WILLIAMS MD
NPI 1558866079
Obstetrics & Gynecology in West Allis, WI

Active since March 27, 2018PECOS EnrolledAccepts Medicare Assignment
8905 W LINCOLN AVE STE 515, WEST ALLIS, WI 53227(414) 328-8650(414) 328-8660 Get Directions Write a Review

NPPES record last updated: July 19, 2025. Verified against the NPPES registry weekly; last sync: October 04, 2026.

Record update history: Nov 23, 2022, Aug 11, 2022, Jun 7, 2019 and 1 more (4 updates tracked since 2018).

About Mercedes M Williams Md NPPES

Official registry information on file with the National Plan and Provider Enumeration System.

MERCEDES M WILLIAMS MD (NPI 1558866079) is an individual obstetrics & gynecology provider in West Allis, Wisconsin, licensed in Wisconsin (74044) and active in the NPI registry since March 2018. She is enrolled in Medicare PECOS, is affiliated with West Allis Memorial Hospital, and maintains a secondary practice location in West Allis.

NPPES Registry Identity

NPI1558866079
Entity TypeIndividualFemale
Primary Taxonomy207V00000X
Provider Legal NameMERCEDES M WILLIAMSCredential: MD
Location Address8905 W LINCOLN AVE STE 515West Allis, WI 53227-2470
Mailing AddressPo Box 735044Chicago, IL 60673-5044 · (800) 326-2250
Phone(414) 328-8650
Fax(414) 328-8660
Sole ProprietorNo
Medical School CMSOtherGraduated 2018
Enumeration DateMarch 27, 2018
Last NPPES UpdateJuly 19, 20254 updates tracked since enumeration
NPPES CertifiedJuly 19, 2025
✔ NPI 1558866079 is a valid, active identifier and passes the ISO check-digit test.

Specialties & Licenses 2

★ Primary SpecialtyObstetrics & GynecologyAllopathic & Osteopathic Physicians
Taxonomy Code207V00000X
License✔ Licensed in WI · 74044
Definition
An obstetrician/gynecologist possesses special knowledge, skills and professional capability in the medical and surgical care of the female reproductive system and associated disorders. This physician serves as a consultant to other physicians and as a primary physician for women.
Also ListedStudent in an Organized Health Care Education/Training ProgramTaxonomy 390200000X
8905 W LINCOLN AVE STE 515, West Allis, WI 53227
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Other Names 1

Former Name (1)Mercedes Williams Weisenberger Md

Secondary Practice Location 1

Location 18901 W Lincoln AveWest Allis, WI 53227-2409 · Phone (414) 328-6000

Other Identifiers 1

Medicaid100205972WI

Accepted Insurance

The full list of accepted plans is on the Insurance tab. Issuers include Anthem Blue Cross and Blue Shield, Aspirus Health Plan, CareSource (Common Ground Healthcare) and more.Insurance ›

Medicare Participation & PECOS CMS

Medicare enrollment, assignment, and ordering and referring status from the CMS PECOS system.

Medicare Enrollment Status

✔

Enrolled in Medicare and accepts Medicare assignment

Mercedes M Williams Md is registered in PECOS and agrees to accept the Medicare-approved amount as full payment. Medicare patients are not billed beyond the standard deductible and coinsurance.

PECOS PAC ID8123379583
PECOS Enrollment IDI20220801001083
Eligible to Order & Refer✔ Part B Labs & Imaging✔ Durable Medical Equipment✔ Home Health Agency✔ Power Mobility DevicesPer the CMS Ordering and Referring file. Eligibility means Medicare pays claims that this provider orders or refers for these categories.

Hospital Affiliations CMS Care Compare

Hospitals where this provider delivers care, identified from recent Medicare claims and place-of-service records.

West Allis Memorial Hospital

Acute Care Hospitals · West Allis, WI
4/5 CMS rating
OwnershipVoluntary non-profit - Private
CMS Certification Number520139
Location8901 W Lincoln AveWest Allis, WI 53227 · Milwaukee County
Emergency services Birthing friendly

Physician Visit Costs CMS claims · ZIP area

Typical Medicare office-visit costs in the 53227 ZIP code area, from fee-for-service claims. These are area statistics, not this provider’s prices; actual charges vary by service and coverage.

New Patient
$123.69 typical visit price
range $53.90 – $163.24
Typical copayment $30.92 (range $13.47 – $40.81)
Most-billed visit code 99204
Established Patient
$67.37 typical visit price
range $17.40 – $133.76
Typical copayment $16.84 (range $4.35 – $33.44)
Most-billed visit code 99213
Amounts reflect what Medicare beneficiaries in this ZIP area are typically charged for office visits. Patients with other coverage should check their individual plans.

Other Providers at the Same Location NPPES 4

Providers registered at the same practice address, or within the immediate area, according to the NPPES registry.

URSULA STAR-ADAMCZYK M.D.
Obstetrics & Gynecology
8905 W LINCOLN AVE STE 515
WEST ALLIS, WI 53227
Milwaukee County (414) 328-8620
SARA M STANENAS D.O
Obstetrics & Gynecology
8905 W LINCOLN AVE STE 515
WEST ALLIS, WI 53227
Milwaukee County (414) 328-8650
KERRY KATZ M.D.
Obstetrics & Gynecology
8905 W LINCOLN AVE STE 515
WEST ALLIS, WI 53227
Milwaukee County (414) 328-8650
AMY LYNN BOHLER FNP-BC
Nurse Practitioner
8905 W LINCOLN AVE STE 515
WEST ALLIS, WI 53227
Milwaukee County (414) 328-8650

Frequently Asked Questions NPPES & CMS

Common questions about this NPI record, answered from the official NPPES registry and CMS datasets shown on this page.

What is Mercedes Williams's NPI number?

The NPI number for Mercedes Williams is 1558866079. It was assigned to this individual provider in the NPPES registry on March 27, 2018. The provider is also known as Mercedes Williams Weisenberger MD.

Where is Mercedes Williams located?

Mercedes Williams practices at 8905 W Lincoln Ave Ste 515, West Allis, WI 53227. The listed phone number is (414) 328-8650.

What is Mercedes Williams's specialty?

The primary specialty registered for this NPI is Obstetrics & Gynecology with taxonomy code 207V00000X.

Is Mercedes Williams enrolled in Medicare?

Yes. Mercedes Williams is registered in the Medicare PECOS system and accepts Medicare assignment, which means accepting the Medicare-approved amount as payment in full for covered services.

What insurance does Mercedes Williams accept?

Health plans from Anthem Blue Cross and Blue Shield, Aspirus Health Plan, CareSource (Common Ground Healthcare), HealthPartners and Quartz and 1 other insurer list Mercedes Williams as in-network in at least one marketplace plan. Coverage varies by plan and year; verify with the insurer or the provider before a visit.

Is Mercedes Williams affiliated with any hospitals?

According to CMS data, Mercedes Williams is affiliated with West Allis Memorial Hospital.

When was this NPI record last updated?

The NPPES record for Mercedes Williams was last updated on July 19, 2025. NPI Profile syncs weekly with the NPPES registry data releases published by CMS. This NPI record was last updated 14 months ago. If this record has changed at CMS more recently, you can request an on-demand re-check against the live CMS registry, directly from this page.