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Dr. J Mark Barnett, MD
Medical Oncology* Age 55
Dr. J Mark Barnett, MD
5.0 (1 Ratings)

Offers telehealth

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Dr. J Mark Barnett, MD is a Medical Oncologist in Longmont, CO.
Dr. J Mark Barnett, MD
5.0 (1 Ratings)
Share
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Link Copied!
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Dr. J Mark Barnett, MD

Medical Oncology* Age 55
Longmont, CO
Accepting new patients
26 years of experience

Offers telehealth

Dr. J Mark Barnett, MD is a Medical Oncologist in Longmont, CO.

About

Dr. Barnett graduated from Southern Illinois University School of Medicine in 2000 and completed a residency at Brown University / Rhode Islan. Dr. J Mark Barnett, MD is a Medical Oncologist in Longmont, CO and has 26 years experience. Dr. Barnett currently practices at Rocky Mountain Cancer Centers-Longmont and is affiliated with Foothills Hospital, AdventHealth Avista, CommonSpirit Longmont United Hospital, CommonSpirit St. Anthony Hospital, CommonSpirit St. Anthony North Hospital, HCA HealthONE Mountain Ridge, Intermountain Health Good Samaritan Hospital, Lutheran Medical Center and UCHealth Longs Peak Hospital. Dr. Barnett has experience treating conditions like Colon Cancer among other conditions at varying frequencies. Dr. Barnett's office accepts new patients and telehealth appointments. Dr. Barnett is board certified in Hematology and accepts multiple insurance plans.

Offers Telehealth

This provider offers telehealth appointments. Call the office to schedule.

Explains Conditions Well

Patients said this doctor explains conditions well.

Trustworthy

Patients said this doctor is trustworthy.

Low Wait Times

Patients are usually seen in 10 minutes or less.

Friendly Staff

Patients said the staff was friendly.

Easy Scheduling

Patients said scheduling was easy.

Experience Check

Enter a condition or procedure
Colon Cancer
Colorectal Cancer
Soft Tissue Sarcoma of Head, Face, and Neck
Colon Cancer
Colorectal Cancer
Soft Tissue Sarcoma of Head, Face, and Neck
Retroperitoneum Cancer
Venous Embolism and Thrombosis
Esophageal Cancer
Vitamin B12 Anemia
Breast Lump
Upper Digestive Tract Cancer
Anemia
  • View other providers who treat Anemia
Pancreatic Cancer
Hemochromatosis
Thyroid Cancer
Testicular Cancer
Metastatic Respiratory System Cancer
Breast Cancer
Liver Cancer
Kidney Cancer
Deep Vein Thrombosis (DVT)
Diffuse Large B-Cell Lymphoma
Multiple Myeloma
Prostate Cancer
Neutropenia
Urinary Tract Cancer
Coagulation Disorders
Uterine Cancer
Pernicious Anemia
Bladder Cancer
Hypogammaglobulinemia
Soft Tissue Sarcoma
Cardiac MRI (Magnetic Resonance Imaging) of Heart or Chest
Primary Hypercoagulable State
Immune Thrombocytopenia
Thrombocytosis
Neuroendocrine Tumors
Myeloproliferative Disorders
Pancytopenia
Liver Biopsy
Acquired Red Cell Aplasia
Acquired Hemolytic Anemia
Acute Monocytic and Monoblastic Leukemia
Acute Myeloid Leukemia Multilineage Dysplasia
Acute Panmyelosis with Myelofibrosis
Acute Promyelocytic Leukemia
Adrenal Gland Cancer
Amyloidosis
Anal Cancer
Antiphospholipid Syndrome (APS)
Benign Mediastinal Tumor
Benign Neoplasm of Brain
Blood Cancer
Breast Carcinoma
Cancer
  • View other providers who treat Cancer
Cancer of Cerebral Meninges
Chordoma
  • View other providers who treat Chordoma
Chronic Myelomonocytic Leukemia
Cutaneous T-Cell Lymphoma
Diffuse Follicle Center Lymphoma
Duodenal Cancer
Endocrine Gland Cancer
Esophageal Diseases
Ewing's Sarcoma
Factor II Deficiency
Factor V Deficiency
Factor VII Deficiency
Factor X Deficiency
Factor XII Deficiency
Factor XIII Deficiency
Follicular Lymphoma Grade 1
Follicular Lymphoma Grade 2
Gastroenterologic Cancer (Colon, Stomach, Esophageal, Liver)
Gastrointestinal Cancer
Gastrointestinal Diseases
Genitourinary Cancers
Gum Cancer
Hematologic Problems
Hypothalamus Cancer
Illeum Cancer
Jejunum Cancer
Leukemia
  • View other providers who treat Leukemia
Leukocytopenia
Leukocytosis
Lymphocytic-Rich Hodgkins Lymphoma
Lymphocytopenia
Lymphocytosis
Lymphoma
  • View other providers who treat Lymphoma
Macroglobulinemia (incl. Waldenstrom's )
Male Breast Carcinoma
Malignancy of Penile Body
Malignant Mediastinal Tumor
Malignant Neoplasm of Gastrointestinal Tract
Malignant Pituitary Gland Tumor
Malignant Pleura Secondary
Mast Cell Diseases
Meningiomas
Multiple Sclerosis (MS)
Myelodysplastic Syndromes
Neoplasm of Gastrointestinal Tract
Nerve Sheath Tumors
Nodular Lymphocyte-Predominant Hodgkin Lymphoma
Nodular Sclerosis Hodgkins Lymphoma
Osteosarcoma of the Spine
Penile Cancer
Penile Carcinoma
Pineal Region Tumors
Pituitary Gland Cancer
Pituitary Tumor
Pleura Cancer
Pleural Cancer
Polycythemia Rubra Vera
Refractory Anemia without Sideroblasts
Secondary Sideroblastic Anemia
Stomach Cancer
Thalassemia
Thymomas
  • View other providers who treat Thymomas
Urethra Cancer
Vulvovaginal Rhabdomyosarcoma
Biopsy of Breast
Cancer Treatment
Chemotherapy
Thoracentesis

Insurance Accepted

* Please verify this information when scheduling an appointment.
  • National (BlueCard Basic) PPO
    WellChoice - U (Select Network)-CO
    University of Colorado Medicare-CO
    Bronze Pathway (Pathway / Small Grp)-CO HMO
    Non-HMO- HSA, HRA and HIA+-CO
    Colorado HMO
    Silver Pathway (Pathway / Small Grp)-CO HMO
    Gold Pathway X (Pathway / Individual)-CO HMO
    WellChoice - C-CO
    Pathway-CO HMO
    Blue Priority-CO PPO
    Silver Pathway (Pathway / Individual)-CO HMO
    Balanced Pathway-CO EPO
    Silver Pathway X (Pathway / Individual)-CO HMO
    CU Health Plan - Extended-CO
    Catastrophic (Individual)-CO PPO
    Indemnity (Traditional)-CO
    Gold Pathway (Pathway / Individual)-CO HMO
    CO Pathway (Select Network)-CO
    Catastrophic Pathway X (Pathway / Individual)-CO HMO
    Bronze Pathway-CO EPO
    Balanced Pathway-CO HMO
    Silver Pathway w/HSA-CO EPO
    University of Colorado Extended PPO
    Colorado PPO
    Healthy Support with HSA 1-CO PPO
    Healthy Blue Priority with HSA 1-CO
    Gold Colorado PPO
    Platinum Pathway-CO EPO
    Healthy Support 1-CO PPO
    Balanced-CO PPO
    Gold Pathway-CO EPO
    WellChoice - C (Select Network)-CO
    University of Colorado High Deductible PPO
    CU Health Plan - Medicare-CO
    National (BlueCard) PPO
    Catastrophic Pathway (Pathway / Individual)-CO HMO
    Silver Pathway-CO EPO
    Lumenos-CO PPO
    CSU Fort Collins-CO
    Colorado College-CO
    Bronze Pathway X (Pathway / Individual)-CO HMO
    Pathway PPO/EPO-CO
    Traditional Network-CO
    MediBlue Plus-CO HMO
    Silver-CO PPO
    Lumenos plans-CO
    CU Health Plan - High Deductible/HSA Compatible-CO
    Platinum-CO PPO
    Bronze Pathway w/HSA-CO EPO
    Bronze Colorado PPO
    WellChoice - H (Select Network)-CO
    WellChoice - U-CO
    Gold Pathway w/HSA-CO EPO
    Healthy Blue Priority 1-CO HMO
    Platinum Pathway (Pathway / Small Grp)-CO HMO
    Colorado POS
    WellChoice - H-CO
    Gold Pathway (Pathway / Small Grp)-CO HMO
    Blue Priority-CO HMO
    Bronze Pathway (Pathway / Individual)-CO HMO
  • Kaiser Permanente
  • HealthyBlue 2.0
    HealthyBlue Advantage
  • First Health (Coventry Health Care) PPO
  • Blue Card PPO
  • Tricare
  • Medicaid
  • Cigna HMO
    Cigna PPO
    LocalPlus
    Cigna
    Open Access Plus
  • UnitedHealthCare
  • Anthem Blue Cross Blue Shield PPO
    Anthem Blue Cross Blue Shield
  • Medicare
  • Aetna
    Aetna HMO
    Choice Plus POS II
    Whole Health Colorado Front Range
  • Rocky Mountain Health Plans
  • Choice Care PPO
    Humana

Locations

  1. 1 Rocky Mountain Cancer Centers-Longmont
    1760 E Ken Pratt Blvd Ste 302, Longmont, CO 80504
    Monday
    08:00 - 17:00
    Tuesday
    08:00 - 17:00
    Wednesday
    08:00 - 17:00
    Thursday
    08:00 - 17:00
    Friday
    08:00 - 17:00
    Saturday
    Closed
    Sunday
    Closed

Patient Satisfaction

Likelihood to recommend Dr. Barnett
5.0
Based on 1 Reviews
5 Stars (1)
4 Stars (0)
3 Stars (0)
2 Stars (0)
1 Star (0)

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Patient Reviews
Jan 31, 2026
As always, he is punctual and very personable. He's always open to answering any questions no matter how of Subject they might be.
— Jan 31, 2026
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Telehealth Options
This provider has not specified a telehealth appointment method. Would you still like to make an appointment with Dr. Barnett?
Call now to make an appointment
(303) 684-1900

About Me

Specialties*
Hematology & Oncology
Medical Oncology
Hematology
Specialties*
  • *Sharecare does not verify qualifications for medical specialties. Please verify your provider's specialty and qualifications directly with your provider and applicable medical board.
Common Questions and Answers
Responses are sourced directly from patients.
Does Dr. Barnett communicate via email?
79 users said yes.
Yes
(79)
No
(20)
Does Dr. Barnett offer telehealth services or virtual visits?
52 users said yes.
Yes
(52)
No
(27)
Does Dr. Barnett offer an online patient portal?
121 users said yes.
Yes
(121)
No
(3)
Does Dr. Barnett have free onsite parking?
145 users said yes.
Yes
(145)
No
(2)
Does Dr. Barnett offer weekend visits?
10 users said yes.
Yes
(10)
No
(60)
Does Dr. Barnett offer evening visits?
10 users said yes.
Yes
(10)
No
(54)
Does Dr. Barnett specialize in working with children or adolescents?
No responses yet.
Yes
(0)
No
(0)
Does Dr. Barnett specialize in working with seniors?
No responses yet.
Yes
(0)
No
(0)
Does Dr. Barnett specialize in couples therapy?
No responses yet.
Yes
(0)
No
(0)
Does Dr. Barnett specialize in working with LGBTQ+ community?
No responses yet.
Yes
(0)
No
(0)
Does Dr. Barnett accept insurance?
No responses yet.
Yes
(0)
No
(0)

Frequently Asked Questions

Find contact information here to make an appointment.

A list of accepted insurance providers is available on the Sharecare insurance check. It is always a good idea to verify your insurance when making an appointment.

New patients are generally accepted by Dr. J Mark Barnett, MD. To arrange an appointment, call the number on Dr. Barnett's profile.

Dr. J Mark Barnett, MD is affiliated with Foothills Hospital, AdventHealth Avista, CommonSpirit Longmont United Hospital, CommonSpirit St. Anthony Hospital, CommonSpirit St. Anthony North Hospital, HCA HealthONE Mountain Ridge, Intermountain Health Good Samaritan Hospital, Lutheran Medical Center and UCHealth Longs Peak Hospital.

Yes, Dr. J Mark Barnett, MD holds board certification in Hematology and Medical Oncology.

Education
Medical Education
  • Southern Illinois University School of Medicine
    2000
Medical Education
Board Certifications
  • Hematology and Medical Oncology
Board Certifications
What’s a board certification and why is it important that my provider has one?

A board certification represents a provider’s dedication to ongoing training in one or more specialties, including the completion of intensive exams. While not all specialties have board certifications, if your provider does have one they’ve taken the extra step to master their specialty and to keep up with the latest advancements in their field.
Residency Hospital
  • Brown University / Rhode Islan
Residency Hospital

Hospital Affiliations

  • Foothills Hospital

    4747 Arapahoe Ave, Boulder, CO

  • AdventHealth Avista

    100 Health Park Dr, Louisville, CO

  • CommonSpirit Longmont United Hospital

    1950 Mountain View Ave, Longmont, CO

  • CommonSpirit St. Anthony Hospital

    11600 W 2nd Pl, Lakewood, CO

  • CommonSpirit St. Anthony North Hospital

    14300 Orchard Pkwy, Westminster, CO

  • HCA HealthONE Mountain Ridge

    9191 Grant St, Thornton, CO

  • Intermountain Health Good Samaritan Hospital

    200 Exempla Cir, Lafayette, CO

  • Lutheran Medical Center

    8300 W 38th Ave, Wheat Ridge, CO

  • UCHealth Longs Peak Hospital

    1750 E Ken Pratt Blvd, Longmont, CO

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