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Gastrointestinal Specialists of Long Island ...

Gastroenterology • Hempstead, NY

About

Gastrointestinal Specialists of Long Island is a small medical practice based in Wantagh, NY (3019 Merrick Rd), serving Wantagh and Malverne (Long Island). The team (3 employees) offers gastroenterology services with a partner-led structure (Zachary Marwil). Key details: - Industry: Medical Practices - Type: Partnership - Contact: 516-785-8075 / 516-785-8139 - Website: gislimd.com - Web presence: low traffic (~124 monthly visits) with typical engagement (3.4 pages per visit) - LinkedIn: company page available If you’re specifically looking for Gastrointestinal Specialists of Long Island in or around Hempstead, note their listed locations are Wantagh and Malverne, NY. No Hempstead office is mentioned in the provided profile.

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Clinic Type

Gastroenterology (multi-location group)

Address

3019 Merrick Rd, Wantagh, NY 11793; 306 Hempstead Ave, Malverne, NY 11565

Phone

516-785-8075

Email

—

Opening Hours

Hours Of Operation: Monday:9:00 AM - 6:00 PM Tuesday:9:00 AM - 6:00 PM Wednesday:9:00 AM - 5:00 PM Thursday:9:00 AM - 5:00 PM Friday:9:00 AM - 3:00 PM Saturday:Closed Sunday:Closed

Website

https://www.gislimd.com/

Services Offered

Upper endoscopy
colonoscopy
office-based capsule endoscopy
breath testing for small intestinal bacterial overgrowth, lactose intolerance, fructose intolerance, and sucrose intolerance

Technology & Equipment

endoscopy center
capsule endoscopy
breath testing

Team

Jeffrey S. Novak, MD, FACG — Physician
Zachary R. Marwil, MD — Physician

Insurance & Payment

We accept most insurance providers.

We accept most insurance providers. For specifics, contact the office.

Not explicitly listed; assume standard insurance and self-pay as applicable

Languages Spoken

not explicitly listed; assume English
not specified

FAQs

What insurances do you accept?

We accept most insurance providers. For specifics, please contact the office.

What are the office hours?

Hours Of Operation: Monday 9:00 AM - 6:00 PM; Tuesday 9:00 AM - 6:00 PM; Wednesday 9:00 AM - 5:00 PM; Thursday 9:00 AM - 5:00 PM; Friday 9:00 AM - 3:00 PM; Saturday: Closed; Sunday: Closed.

Where are the offices located?

Wantagh office: 3019 Merrick Rd, Wantagh, NY 11793; Malverne office: 306 Hempstead Ave, Malverne, NY 11565.

What are the contact details for appointments?

Phone: 516-785-8075; Fax: 516-785-8139.

Photos

What Patients Say

Overall sentiment across review platforms: positive

Birdeye: 5 out of 5 stars (aggregated) (222 reviews)
Wheree: 8.8 out of 10
Healthgrades (Dr. Jeffrey Novak): 4.1 out of 5 (14 reviews)

Patients praise

Compassionate and professional doctors with excellent bedside manner
Thorough explanations of conditions and treatment plans
Friendly, welcoming, and efficient office staff (majority of reviews)
Clean and well-organized facilities

Common complaints

Occasional long wait times
Isolated reports of rude or untrained office staff

"Dr. Marwil takes time to answer your questions & has great bedside manner. Office staff very pleasant & efficient!"

— Gastrointestinal Specialists of Long Island Testimonials Page

"Dr. Novak is very patient, honest and does not talk over your head. He takes your concerns very seriously and offers candid opinions when needed."

— LocalityBiz Review

"Dr. Novak is wonderful. He was recommended by a friend a couple of years ago. Very satisfied with him. His staff is another thing however very rude and has no customer training."

— Healthgrades Review

Synthesized from public review platforms as of Jul 11, 2026 — sources: [1][2][3][4].

In the News

Dr. Xinjun Zhu, MD - Gastroenterologist in Albany, NY — May 14, 2026
Shahzad Iqbal, MD | Catholic Health | Long Island - Babylon, NY - Gastroenterology - Schedule Online — Mar 22, 2026
Dr. Debra Tundis, MD - Anesthesiologist in Massapequa, NY — May 14, 2026
Isaiah Paul Schuster, MD | Catholic Health | Long Island - Greenvale, NY - Gastroenterology - Schedule Online — Mar 25, 2026
Dr. Emily Glazer, MD - Gastroenterologist in Wading River, NY — May 14, 2026

Information sourced from the clinic's website as of July 11, 2026.

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