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    Jay Guan, MD

    4.4 (8 reviews)
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    Very professional, quick to diagnose and treat my issues, and helped address my messages and concerns in a timely fashion.

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    Karen Simon, MD - Karen Simon, MD

    Karen Simon, MD

    3.0(17 reviews)
    7.5 mi

    I received email from Dr Simon office to scheduled my appointment. Which I did called last Aug 2025…read moreand they scheduled me for Dec 12 consultation. Comes this day went to Wenkle way turned out the office moved, looked on line for new office at Gonzales . Went there to find out they canceled my appointment because my phone number was incorrect. I do not have a valid phone on there file.

    I am literally in tears writing this review. I cannot make up the way I was so badly treated from…read morethis so called " health CARE" provider. Please young ladies beware!!! I was referred to this office by my main physician back in October of 2024. I went through the whole process of being approved, which took months (totally normal). Once April comes around they finally call me to set up an appointment and just like everyone else in America I was working when they called. They left me a voicemail and I called them back everyday for 3 weeks! Yes 3 weeks, I have call logs to prove it, I finally get an answer and schedule an appointment. Once it's time for the procedure I was instructed to get one of their kits . I arrived to their office off of Lombard in Oxnard, ca. The office was closed down and no one was there. They failed to mention to their patients that they were moving locations. Thank god they had the decency to leave a note because I would've been so confused (lack of communication). I go the other office and the girl in there was so rude she literally was treating me like I was a disease. Had a blank stare when I asked questions and just handed me the kits not explaining anything to me! This is all new to me, I am 35 years old I shouldn't even be in this office because I feel I am too young to be having issues. So I am already feeling scared and completely helpless and to come into this office and get treated like a disease is completely un empathetic . These people are supposed to have compassion and empathy. This girl with colored eyes didn't care if I am completely scared or am feeling helpless. On top of all of this I have my 2 year old son with me trying to be friendly with her and she is just giving him dirty looks. So I left upset, not feeling confident at all about the place that has me under their care, and full of unanswered questions. Now it's over a month after the procedure and I have crickets. No follow up appointment, no confirmation that I am cancer free, most importantly, no confirmation that I am going to be okay. So I call today trying to get some answers because obviously the issues I have aren't going away with just a biopsy. It took me 4 calls today to get ahold of someone to the point where I am literally crying my eyes out because all I want are some answers. On the 4th call they finally transferred me to the nurse who works with the actual doctor and she told me that everything is in my portal. That's funny I didn't even know I had a portal. So they send my information to a place where I have to figure out on my own with documents that I can't understand. When I asked her to please explain the results because this is all terminology that I do not understand because this is not my line of work. She said just come back in 10 years. So what I am getting from all of this is, I am not worth anymore money to them so they not only didn't take the time to call me about my results that I have been so desperately waiting for but now I realize that I am worth no more effort to them because of the results. These so called "healthcare" providers who are literally paid to care about people and their state of being couldn't care less. They couldn't even call me to tell me they sent me a prescription. I still till this day don't know what it's for. I pray these people gain some empathy for people who walk through their doors because I was treated less than human. My employer who I have been with for 15+ years pays a pretty penny for my health insurance so this isn't something for free! If these are the people who are in charge of peoples health and well being, god help us all.

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    Karen Simon, MD
    Karen Simon, MD
    Karen Simon, MD

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    Ventura County Gastroenterology Medical Group - New location yay

    Ventura County Gastroenterology Medical Group

    2.8(8 reviews)
    0.0 mi

    My review is for this gastroenterology office and their neighboring (next door) outpatient surgery…read morecenter. Seeing the lower reviews I wanted to come on to add some clarity and kudos where I can. Again, not always the kind of place a person wants to have to come but when navigating your healthcare needs it's important to find a place with professional staff, established doctors and an overall office that feels clean, organized and calm. I can understand some of the lower reviews for the wait times/hospitality at the main office. I've been here about three times and one out of the three times my experience was a little slow unnecessarily it felt like. But I just accepted that they were busy and sometimes there are things going on behind the scenes that those of us in the lobby can't always comprehend. I found my interactions with the front desk staff to be to the point, and while sometimes a little slow with the paperwork or getting me my materials, I still felt like it was a professional setting. On the back end all of the medical staff are really great in my opinion. The nurse practitioners that I have seen and the additional aids/surgery schedulers were all wonderful. Everyone was very friendly and I felt like my nurse practitioner was very kind and patient with me as we navigated some of my healthcare issues. I've been established with Dr. Rojany at this office over the years and he's honesty wonderful. Great beside manner, thorough, kind, attentive and makes your experience feel supportive. While my medical consultations with him have been sporadic over the years he has always been great and I would highly recommend him. I was re-introduced to him as I had to go into the surgery center for an outpatient procedure. Again, he was very kind and reassuring, and the process went smoothly for my procedure. To the nurses and staff working the surgery center next-door, I would give them 10/10 stars if that was a thing! Full transparency I'm a very emotionally medically fragile person lol from blood draws, to just being in a medical setting, I usually cry and have a lot of anxiety. Going in for a procedure where I was going to be given anesthesia was very anxiety provoking to me, but all of the staff that helped me were so kind and understanding. They made me feel safe, validated my experience, but reassured me that everything was going to go fine and just had really positive bedside manner to help get me to a place that I could calm down and get through with our appointment. There were so many lovely ladies that helped me. I'm sorry that I can't recall everyone by name, but I do think they just have an amazing stellar team here that if you have to have some Gastro follow up or procedures done this is the place to come in my opinion. Couldn't thank them enough for their kindness, care and professionalism.

    As I sit waiting on hold, 13 minutes so far, disconnected once, I have to agree with the "poor"…read moreservice from the staff comments. I've been a patient of Dr Miller's for years and he is a consummate professional. However, it is frustrating not to be able to make an appointment. Another time I was waiting for an MRI while the technician tried to reach the office, and it took 28 minutes on hold before anyone answered! Simply unprofessional since "UNIO Specialty Care" took over. I believe it is time to seek out another practice. This group must be understaffed and way too busy.

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    Ventura County Gastroenterology Medical Group - This could be you

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    John C Billesdon, MD - John C Billesdon, MD

    John C Billesdon, MD

    3.0(2 reviews)
    0.0 mi

    I'm so surprised by the other glowing reviews. Dr. Billesdon is the second worst doctor I've ever…read moredealt with. I told him my diverticulitis was flaring up. He didn't examine me at all, just told me to start taking 15mg of fiber a day. After one week I was doubled over in pain and severely constipated. But, every time I called to speak with the doctor, I couldn't. I spoke with assistants, who spoke with nurses who spoke to a doctor (not sure which doctor) and relayed messages back to me. One time I left a message and no one called back. By week two I was vomiting and in terrible pain. Still couldn't talk to Dr Billesdon. Finally, I went to the ER where I was diagnosed with an acute diverticulitis attack, put on two antibiotics and given Percocet for my pain. And told to STOP taking the fiber, since it had the opposite effect of what it was supposed to do. Now, it would have been grand if Dr Billesdon could have just spoken to me and told me to stop the fiber the first time I called. Don't waste your time here, there are better GI doctors nearby.

    Thanks to a rare disorder, I must have not only an annual colonoscopy, but an EGD, which means the…read morewhole route from mouth to tail end. I must also avoid sunlight, even in the recovery room. Members of the staff jump right in to help me with this. The doctors' assistants are wonderful and cheerful. Dr. Billesdon himself is very thorough and explains his findings very clearly and instructs me how to address various concerns. Their follow-up clearly shows how thoroughly they handle each patient. I'm fortunate to have been referred to this group.

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    John C Billesdon, MD
    John C Billesdon, MD
    John C Billesdon, MD

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    Donald Miller, MD

    Donald Miller, MD

    3.4(5 reviews)
    0.0 mi

    Really like this office and Dr Miller. Scheduling appointments and getting lab work orders is done…read morewhile you're there and it's very convenient. Dr Miller and the staff are always friendly and positive. I have always had a good experience

    Office experience was totally disrespectful, unprofessional and completely unorganized and I…read morepolitely let Dr. Miller know how I was treated and he seems to do nothing about it. It's obvious in the other persons review and mine. It seems as if the office possibly tried to falsely and charge me and my insurance and said I saw the doctor when receiving a test which I never saw any doctor on that day of the test.I had to contact my insurance company for them to refund the co pay off my bill. As well, they had a female assistant do my scan that I later found out was not a certified tech to do the test nor did they have a certified tech in the room with us. When I asked her how long she was certified to do the scans, she told me after I was on the table that all the techs were not there that day, but she said don't worry that she had seen many of them done so she could do it. I wasn't happy about it ,but I had no choice I was already on the table. Then when I received my medical testing paperwork it said a man's name under the technician that supposedly did my test though it wasn't him nor a certified person that performed my test. Then I tried to contact the office manager Elizebeth through emails and telephone calls politely and never received a response nor a call back. I would never step my foot in that office again nor recommend them. I ended up going to another wonderful gastroenterologist where his team and office treat patients with kindness,professionalism, and respect.

    Justin Marasigan, DO

    Justin Marasigan, DO

    1.0(1 review)
    0.0 mi

    Dr Marasigan is the worst excuse for a doctor I have ever met. Left me to suffer in pain for months…read morewithout listening to me. Would not refer me to medical center even when I begged. Always takes an eternity to get an appointment. Staff is horrifying. They hang up on you, never call back or just transfer you to a dial tone. You just cannot speak to anyone there as the wait time are almost an hour to make an appointment. I even tried in desperation used the portal to request an appointment couple weeks ago and just received a message from the doctor - he doesn't care.... Even a little. Not one care given. Cannot believe he is licensed. Please never meet this guy! Run! You are better off doing it yourself gasto.

    From the owner: Dr. Justin Marasigan is a Board-Certified Gastroenterologist who was raised in the Los Angeles…read morearea. He earned his undergraduate degree from the University of Southern California and his medical degree from Kirksville College of Osteopathic Medicine in Missouri. Dr. Marasigan went on to complete his Internal Medicine Residency in the Detroit area and his Gastroenterology specialty training in Erie, Pennsylvania. He applied a variety of experiences from rural offices to large academic centers throughout Western Pennsylvania and Eastern Ohio. Prior to joining inSite Digestive Health Care in Ventura County, Dr. Marasigan was practicing Gastroenterology for 7 years in Washington State.

    Jay Guan, MD - gastroenterologist - Updated May 2026

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