Browse specialties
Chiropractors
Dentists
Dermatologists
Ear, Nose & Throat Doctors
Endocrinologists
Eye Doctors
OBGYNs
Ophthalmologists
Optometrists
Orthopedic Surgeons
Podiatrists
Primary Care Doctors
Psychiatrists
Psychologists
Therapist-Counselors
See all specialties A-Z
Zocdoc
HomeAbout usPressCareersHelp
Contact
service@zocdoc.com855-962-3621
Discover
The Paper Gown: Stories for and about patientsThe Script: Insights for doctorsCommunity StandardsData and privacyVerified reviewsTech BlogNew
Are you a top doctor or health service?
Try Zo, your AI Phone AssistantList your practice on ZocdocLearn about Zocdoc for Health SystemsBecome an EHR partner
Insurance Carriers
Top Specialties
Welcome to Zocdoc!
Book local doctors who take your insurance
Sign up
For providers
Grow your practice
For patients
Zocdoc
HomeAbout usPressCareersHelp
Contact
service@zocdoc.com855-962-3621
Discover
The Paper Gown: Stories for and about patientsThe Script: Insights for doctorsCommunity StandardsData and privacyVerified reviewsTech BlogNew
Are you a top doctor or health service?
Try Zo, your AI Phone AssistantList your practice on ZocdocLearn about Zocdoc for Health SystemsBecome an EHR partner
Insurance Carriers
Top Specialties
HelpList your practice on Zocdoc
Sign up
Dr. John Lah, MD

Dr. John Lah, MD

Gastroenterologist
3851 Katella Ave, Ste 205, Los Alamitos, CA
4.66
“DrJohn Lah was very iinformative during my appointment. He answers all the health issues I asked him. He assisted me to the front desk for my next sppointment.”
Aurea G.November 6, 2025
Excellent wait time
97% of patients waited less than 30 minutes
New patient appointments
Appointments available for new patients on Zocdoc

Book an appointment for free

The office partners with Zocdoc to schedule appointments

Scheduling details

  1. See if they are in network

Available appointments

What patients are saying

Overall rating

4.66

Average wait time

4.70

Bedside manner

4.79
“DrJohn Lah was very iinformative during my appointment. He answers all the health issues I asked him. He assisted me to the front desk for my next sppointment.”
Aurea G.November 6, 2025
“Dr. Lah was obviously knowledgeable, honest and a good communicator. He was clear that he wanted to review my files from my recently-retired gastroenterologist before commenting on my prior procedures. I felt like I was in good hands.”
Initials hiddenSeptember 17, 2025

About Dr. John Lah

Dr John J. Lah is a highly skilled, experienced gastroenterologist and former chief of GI at PIH Whittier. There he served on clinical faculty for the family practice residency for over 13 years. Prior to his Whittier legacy, he was the associate chief of GI at Kaiser Permanente in Walnut Creek. He completed his GI fellowship at UC Irvine where he developed his interventional endoscopic skills including endoscopic mucosal resection of large polyps, luminal stent placement and ERCP. He has performed over 20,000 endoscopic procedures with minimal complication rates. He received multiple teaching awards as faculty for the family practice residency at PIH Whittier and values communicating well with his patients and colleagues. He enjoys helping patients get a better understanding of their conditions and being able to provide practical, efficient solutions for their care. Dr. Lah is hard working, conscientious, and committed to providing high quality, compassionate care. He remains up to date with most recent advances in gastroenterology and will be actively involved with clinical research related to exciting new medications and diagnostics technologies. He looks forward to serving the needs of his patients and community.

Is this doctor in your insurance network?

Enter your insurance carrier and plan

  1. choose insurance

In-network insurances

99% of patients have successfully booked with these insurances
Aetna
BlueCross BlueShield
Cigna
Medicare
UnitedHealthcare
100+ more in-network plans

Areas of expertise

This doctor's experience enhances their expertise in similar cases. Below are the conditions or surgeries they treat most frequently.
Acid reflux
Upper GI endoscopy
Colonoscopy
Acid reflux
Upper GI endoscopy
Colonoscopy

Office locations

United Medical Doctors - Los Alamitos, Katella Ave (1 of 2)
3851 Katella Ave, Ste 205, Los Alamitos, CA 90720
Get directions
United Medical Doctors (2 of 2)
3840 Woodruff Ave, Ste.206, Long Beach, CA 90808
Get directions
1 of 2

Education and background

Practice names

Board certifications

  • Gastroenterology (American Board of Internal Medicine)

Education and training

  • Medical School - New York Medical College, Doctor of Medicine
  • University of California, Irvine, Fellowship in Gastroenterology
  • University of California, Irvine, Residency in Internal Medicine
  • University of California San Diego (Bachelor's)

Languages spoken

  • English

Provider's gender

Male

NPI number

1437221272

Patient reviews

All reviews have been submitted by patients after interacting with the practice.
Overall rating
4.66
Wait time
4.70
Bedside manner
4.79
Trust Banner Shield
Your trust is our top concern, so providers can't pay to alter or remove reviews. We also don't publish reviews that contain any private patient health information. Learn more here
67 reviews
Most relevant
My visit was productive and focused on my needs and next steps for my condition.
Verified patient
Dr. Lah seemed very competent and knowledgeable. My wife was with me and she saw it the same way. I'm glad we found him.
Verified patient
The doctor is a great listener, and he communicates with the patient very well with professional expertise
Dr Lah was professional and friendly. He explained everything and was able to provide the needed care.
Verified patient
Super helpful and answered all our questions with ease!
Verified patient
Doc was great, got me in right away, and made it as comfortable as could be expected.
Verified patient
Made me feel very at ease and very understanding of my condition
Had a great appointment , would use this service again
Verified patient
He knew his stuff & we’re trying something new for me
Verified patient
Amazing professional. Very friendly and communicator
Verified patient
DrJohn Lah was very iinformative during my appointment. He answers all the health issues I asked him. He assisted me to the front desk for my next sppointment.
Verified patient
Dr. Lah was obviously knowledgeable, honest and a good communicator. He was clear that he wanted to review my files from my recently-retired gastroenterologist before commenting on my prior procedures. I felt like I was in good hands.
This visit was one of the best experiences with a physician appointment that I have ever had. I have already referred others to him.
Verified patient
Dr Lau was very methodical and provided as me details as possible to make me a more informed patient. I would definitely recommend Dr. Lau.
Verified patient
Dr. Lah was excellent! I would highly recommend him. I appreciate that he listened to me and that he appeared to genuinely care. I like the fact I didn’t feel rushed.
Verified patient
Verified patient
Verified patient
Verified patient
Verified patient
Verified patient
Verified patient
Frequently asked questions

How soon can I make an appointment with Dr. John Lah?

Generally, Dr. John Lah has appointments available on Zocdoc within 1 week. You can see Dr. Lah's earliest availability on Zocdoc and make an appointment online.

Is Dr. John Lah accepting new patients?

Dr. John Lah generally accepts new patients on Zocdoc. You can see Dr. Lah's earliest availability on Zocdoc and schedule an appointment online.

Does Dr. John Lah accept my insurance?

Choose your insurance plan to verify if Dr. Lah is in-network.

Can I make an appointment with Dr. John Lah online?

Yes, you can make an appointment online with Dr. Lah using Zocdoc. It’s simple, secure, and free.

What practice does Dr. John Lah work with?

Where is Dr. John Lah's office located?

Dr. John Lah has 2 office locations, including in Los Alamitos and Long Beach, view full addresses on Dr. Lah's profile.

Which board certifications does Dr. John Lah have?

Dr. John Lah is certified by Gastroenterology (American Board of Internal Medicine).

What are common reasons for patients to see Dr. John Lah?

Dr. John Lah frequently sees patients for Abdominal Pain, Colonoscopy, Gastroenterology Consultation, Hemorrhoids, and Illness. You can see other visit reasons for Dr. John Lah on their profile.

What languages does Dr. John Lah speak?

Dr. John Lah speaks English.

How do patients rate Dr. John Lah in reviews?

67 patients have reviewed Dr. John Lah. The overall rating for this doctor is 4.66/5. They have a 4.79/5 rating for bedside manner and a 4.7/5 rating for wait time. You can read individual reviews and ratings on their profile.

Find doctors