Mark Grossklaus, MD
NPI 1255403101 · Family Medicine Physician · Waukesha, WI
Enrolled with Medicare as Practitioner - Family Practice · source: CMS PECOS Public Provider Enrollment (2026.04.01)
Mark Grossklaus, MD is a Family Medicine Physician provider in Waukesha, WI (NPI 1255403101).
Provider details
- NPI number
- 1255403101
- Entity type
- Individual
- Primary specialty
- Family Medicine PhysicianAllopathic & Osteopathic Physicians
- Credential
- MD
- Sex
- Male
- Sole proprietor
- No
- License
- 36936 (WI)
Specialties & taxonomies
Allopathic & Osteopathic Physicians
Profile Score
A profile completeness & documented-activity index — NOT a quality, outcomes, or patient-satisfaction rating.
- Registry tenure28% of score
19 yrs in NPPES registry
- Profile completeness28% of score
100% of core fields populated
- Practice footprint17% of score
1 documented practice location
- Medicare service volume (vs. specialty peers)28% of score
3,822 Medicare services, 2024 (ranked within specialty)
Medicare volume is ranked against active providers in the same specialty. Signals a provider has no public data for (e.g. Medicare claims) are left out of the score entirely — never counted as zero — so providers without that data are not penalized. See the full formula and weights in our methodology.
What this provider does (Medicare)
Based on Medicare fee-for-service claims, 2024; not all care is captured.
| Service (HCPCS) | Medicare services | Typical Medicare-allowed (2024) |
|---|---|---|
| Insertion of Needle Into Vein for Collection of Blood Sample36415 | 3,232 | $9 |
| Established Patient Office Or Other Outpatient Visit With Moderate Level of Decision Making, If Using Time, 30 Minutes Or More99214 | 197 | $120 |
| Annual Wellness Visit, Includes a Personalized Prevention Plan of Service (pps), Subsequent VisitG0439 | 112 | $122 |
| Anticoagulant Management of Patient Taking Warfarin93793 | 100 | $11 |
| Blood Test, Clotting Time85610 | 86 | $4 |
| Established Patient Office Or Other Outpatient Visit With Low Level OD Decision Making, If Using Time, 20 Minutes Or More99213 | 39 |
What this provider prescribes (Medicare Part D)
Top drugs by Medicare Part D claim volume, 2024 · 73 distinct drugs on file.
| Drug | Part D claims (2024) | Beneficiaries |
|---|---|---|
| Atorvastatin Calcium | 463 | 133 |
| Amlodipine Besylate | 339 | 105 |
| Rosuvastatin Calcium | 264 | 92 |
| Lisinopril | 230 | 76 |
| Pantoprazole Sodium | 174 | 59 |
| Omeprazole | 165 | 47 |
| Levothyroxine Sodium |
Practice location
Mailing address
Registry dates
- Enumerated
- 2006-11-15
- Last updated
- 2013-08-01
Frequently asked questions
- What is Mark Grossklaus's NPI number?
- Mark Grossklaus's National Provider Identifier (NPI) is 1255403101, a unique 10-digit ID issued by CMS for use in standard healthcare transactions.
- What is Mark Grossklaus's specialty?
- Mark Grossklaus is listed in the NPPES registry with a primary specialty of Family Medicine Physician (Allopathic & Osteopathic Physicians).
- Where is Mark Grossklaus located?
- Mark Grossklaus's practice location on file with NPPES is 717 W Moreland Blvd, Waukesha, WI 53188-2432.
- What is Mark Grossklaus's phone number?
- The practice phone number listed in the NPPES registry for Mark Grossklaus is (262) 542-9100.
- Does Mark Grossklaus accept Medicare?
- Mark Grossklaus is approved to bill Medicare according to CMS PECOS enrollment data (2026.04.01). Confirm current participation with the provider before scheduling.
- Is Mark Grossklaus's NPI active?
- Yes — Mark Grossklaus's NPI (1255403101) is active in the NPPES registry as of the last update on 2013-08-01.
Source: CMS NPPES Data Dissemination (June 2026). NPI Central is not affiliated with CMS. Data is provided as-is from the public registry.