Mark Fesler, MD
NPI 1235204066 · Hematology & Oncology Physician · Saint Louis, MO
Enrolled with Medicare as Practitioner - Hematology/Oncology · source: CMS PECOS Public Provider Enrollment (2026.04.01)
Mark Fesler, MD is a Hematology & Oncology Physician provider in Saint Louis, MO (NPI 1235204066).
Provider details
- NPI number
- 1235204066
- Entity type
- Individual
- Primary specialty
- Hematology & Oncology PhysicianAllopathic & Osteopathic Physicians
- Credential
- MD
- Sex
- Male
- Sole proprietor
- No
- License
- 43133 (CO)
Specialties & taxonomies
Allopathic & Osteopathic Physicians
Allopathic & Osteopathic Physicians
Profile Score
A profile completeness & documented-activity index — NOT a quality, outcomes, or patient-satisfaction rating.
- Registry tenure25% of score
19 yrs in NPPES registry
- Profile completeness25% of score
100% of core fields populated
- Practice footprint15% of score
1 documented practice location
- Medicare service volume (vs. specialty peers)25% of score
1,452 Medicare services, 2024 (ranked within specialty)
- Open Payments transparency10% of score
Has Open Payments disclosures (2024)
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 .
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) |
|---|---|---|
| Established Patient Office Or Other Outpatient Visit With High Level of Medical Decision Making, If Using Time, 40 Minutes Or More99215 | 864 | $173 |
| Subsequent Hospital Care With Moderate Levelof Medical Decision Making, If Using Time, at Least 50 Minutes99233 | 421 | $114 |
| Initial Hospital Care With Moderate Level of Medical Decision Making, If Using Time, at Least 75 Minutes99223 | 124 | $166 |
| New Patient Office Or Other Outpatient Visit With a High Level of Medical Decision Making, If Using Time, 60 Minutes Or More99205 | 28 | $212 |
| Established Patient Office Or Other Outpatient Visit With Moderate Level of Decision Making, If Using Time, 30 Minutes Or More99214 | 15 | $123 |
Typical Medicare-allowed amounts for these services range $114–$212 (2024). The Medicare-allowed amount is what Medicare recognizes for a service under fee-for-service — a reference figure for 2024, and not what you would be billed. Medicare Part B covers roughly an eighth of all NPIs (65+ skew); services with fewer than 11 beneficiaries are suppressed by CMS. Source: CMS Medicare Physician & Other Practitioners, by Provider & Service.
What this provider prescribes (Medicare Part D)
Top drugs by Medicare Part D claim volume, 2024 · 40 distinct drugs on file.
| Drug | Part D claims (2024) | Beneficiaries |
|---|---|---|
| Valacyclovir Hclbrand: Valacyclovir | 355 | 85 |
| Lenalidomidebrand: Revlimid | 169 | 23 |
| Sulfamethoxazole/Trimethoprimbrand: Sulfamethoxazole-Trimethoprim | 165 | 42 |
| Acyclovir | 162 | 36 |
| Venetoclaxbrand: Venclexta | 159 | 32 |
| Lenalidomide | 125 | 17 |
| Prednisone | 115 | 31 |
Transparency — industry payments
Based on CMS Open Payments, 2024; not all care is captured.
$192,797 across 134 records (Open Payments 2024)
Open Payments discloses payments and transfers of value (meals, travel, consulting, research, royalties) from drug and device makers to providers. This is a transparency signal, not a verdict — such payments are legal and common, and their presence is neither an endorsement nor a criticism. Source: CMS Open Payments, program year 2024.
Practice location
Mailing address
Registry dates
- Enumerated
- 2006-11-21
- Last updated
- 2021-03-29
- Certified
- 2021-03-29
Frequently asked questions
- What is Mark Fesler's NPI number?
- Mark Fesler's National Provider Identifier (NPI) is 1235204066, a unique 10-digit ID issued by CMS for use in standard healthcare transactions.
- What is Mark Fesler's specialty?
- Mark Fesler is listed in the NPPES registry with a primary specialty of Hematology & Oncology Physician (Allopathic & Osteopathic Physicians).
- Where is Mark Fesler located?
- Mark Fesler's practice location on file with NPPES is 3655 Vista Ave, Saint Louis, MO 63110-2539.
- What is Mark Fesler's phone number?
- The practice phone number listed in the NPPES registry for Mark Fesler is (314) 977-4340.
- Does Mark Fesler accept Medicare?
- Mark Fesler is approved to bill Medicare according to CMS PECOS enrollment data (2026.04.01). Confirm current participation with the provider before scheduling.
- Is Mark Fesler's NPI active?
- Yes — Mark Fesler's NPI (1235204066) is active in the NPPES registry as of the last update on 2021-03-29.
Source: CMS NPPES Data Dissemination (June 2026). NPI Central is not affiliated with CMS. Data is provided as-is from the public registry.