William C. Bayer, MD

4.9

1888 ratings Read Reviews

Northwestern Medicine Regional Medical Group

Primary Specialty

Endocrinology

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Education

Medical Education:: MD, Loyola University Stritch School of Medicine - 1986
Residency:: Loyola University Medical Center - 1989
Fellowships:: Loyola University Medical Center - 1991

Board Certifications

American Board of Internal Medicine - Internal Medicine (Certified)
American Board of Internal Medicine/Endocrinology, Diabetes and Metabolism - Endocrinology, Diabetes & Metabolism (Certified)

Practice Groups and Affiliations

Medical Group:: Northwestern Medicine Regional Medical Group
Alignment Category:: Northwestern Medicine Physician Network
On Medical Staff At:: Central DuPage Hospital

Ratings and Reviews

At Northwestern Medicine, our patient’s feedback is important to us. While different care providers have their own unique strengths, we strive to be as transparent as possible with our quality of care.

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Overall Rating

4.9

4.9

1888 Ratings

Reviews from Patients

100 Most Recent Reviews

Reviews from Patients

100 Most Recent Reviews

February 26, 2026

5.0

Dr. Bayer is the best. Absolutely love him. He's my favorite doctor. He always explains things in detail and is very down to earth.

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February 25, 2026

5.0

He was professional, friendly, and took the time I needed with him. It was an initial consultation and he made sure to answer all of my questions. I also appreciate his honest feedback.

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February 25, 2026

5.0

Professional, knowledgeable, congenial

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February 23, 2026

5.0

Dr Bayer is very thorough & takes his time to really explore issues or concerns. He has great follow thru on medical issues

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February 23, 2026

5.0

He's a great doctor. Excellent care in managing my diabetes

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February 22, 2026

5.0

Dr. Bayer was very thorough. He thinks outside the box, and sets up a plan taylored to you.

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February 21, 2026

5.0

Caring clear and thorough

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February 20, 2026

5.0

Excellent care

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February 17, 2026

5.0

Dr.Bayer is kind, patient, engaging, a great listener and he's willing to consider alternatives if something doesn't seem to be working. He's great!

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February 16, 2026

5.0

He knows his stuff. He not only knows about the thyroid but takes time to get to know his patients. I have been working with him for a couple of decades and would hate to see him leave as I do not think he can be replaced. He truly is a down to earth guy who knows his stuff about not only thyroid but diabetes. My mom sees him as well and he is great with her as well. He also works with my other doctors as I see many others for multiple autoimmune disorders

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February 11, 2026

5.0

Explains everything very clearly and listens

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February 11, 2026

5.0

Dr Bayer is very thorough, and is always caring, listening and addressing all my concerns

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February 04, 2026

5.0

I have never felt better since under the care of Dr. Bayer!

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February 03, 2026

5.0

Friendly and knowledgeable!! Thanks!!

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February 03, 2026

5.0

Dr. Bayer is in his own category! He is extremely intelligent and knows his Craft. He relates so well to patients. I trust his judgment implicitly.

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February 03, 2026

5.0

He explains, he doesn't rush Very good bedside manner

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February 02, 2026

5.0

He made me feel like an individual rather than merely a collection of test results. He looks at all the numbers, is very thorough, yet sees you as a real person

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January 31, 2026

5.0

Friendly and knowledgeable

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January 31, 2026

5.0

I highly recommend Dr. Bayer to anyone seeking excellent endocrinology care.

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January 30, 2026

5.0

Best Dr out there

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January 28, 2026

5.0

very thorough, personable, experienced

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January 27, 2026

5.0

Dr. Bayer is very personable and thorough. He always checks on how my other conditions are doing and that I am following up with my other doctors.

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January 21, 2026

5.0

Excellent doctor. He Really listens and cares.

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January 21, 2026

5.0

Always very caring and helpful to maintain my health

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January 20, 2026

5.0

Dr Bayer is always professional, personable, caring, thorough, and respectful.

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January 10, 2026

5.0

Been a patient for over 25 years

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January 06, 2026

5.0

Dr. Bayer is sharp and positive. He does not push medication as a quick fix, which I appreciate greatly. I feel like he is more interested in what is right and best for me.

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January 05, 2026

5.0

I been going to this practice almost my whole life. I moved to TN (part time) and still came to Dr Bayer. Now I drive an hour to see him!

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December 28, 2025

5.0

When I first did a "meet-and-greet" with Dr. Bayer, I was extremely impressed with him. His knowledge of my condition was amazing to me because my condition was supposedly rare. He is very caring and concerned with how his patients are doing. He is very thorough. His main concern is helping his patients feel better. I have come a long way in my health goals because of Dr. Bayers' support.

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December 24, 2025

5.0

For patient care and experience, he personifies a caring and very capable physician. He could be a wonderful mentor.

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December 23, 2025

5.0

Dr. Bayer is so professional, caring and thorough.

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December 23, 2025

5.0

Love him he's very caring and listens

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December 22, 2025

5.0

FANTASTIC!

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December 18, 2025

5.0

I've been working with DR Bayer since 1999, long before NW Med

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December 18, 2025

5.0

He is the best! So thorough. Cares about me & gives me his full attention.

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December 13, 2025

5.0

He cares and listens to /for his patients.

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December 09, 2025

5.0

He takes the time to consider all aspects of your overall health and medical conditions not just Diabetes

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December 08, 2025

5.0

I would recommend him because he is knowledgeable and interested in his 0atien5s. But I hesitate to recommend him because it is already difficult to get an appt with him.

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December 08, 2025

5.0

Concern for patient and their particular needs. Friendly and competent.

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December 08, 2025

5.0

Dr Bayer is an exceptional doctor. Knows his stuff. Professional and friendly. Not many like him.

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December 08, 2025

5.0

I have seen Dr. Bayer for my thyroid condition for 25 years. His knowledge, compassion and expertise have guided me through my journey. One of the best medical professionals I have ever dealt with. Top in his field!

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December 05, 2025

5.0

Dr Bayer put me on course to get a good A1C. I spent many years trying other drugs with no success.

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December 05, 2025

5.0

Endocrinologist Dr. William Bayer is an excellent Endocrinologist! The very best!

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December 03, 2025

5.0

Doctor Bayer is the best. I like that my illness is being treated and I am getting better.

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December 02, 2025

5.0

Good doctor Easy to talk to Friendly

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November 25, 2025

5.0

Wouldn't see anyone else

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November 25, 2025

5.0

I like Dr Bayer- he's thorough and personable

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November 24, 2025

5.0

I recommend him all the time. He's knowledgeable and kind.

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November 24, 2025

5.0

He understands his patients and listens well. He continues to offer the best for his patients in terms of discussions and being included in their medical care.

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November 24, 2025

5.0

He takes his time with me and answers all my questions.

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November 19, 2025

5.0

Also, Dr Bayer includes me in decisions & makes me feel comfortable while talking with him & encouraged!

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November 16, 2025

5.0

Excellent doctor

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November 11, 2025

5.0

Good bedside manner

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November 11, 2025

5.0

He listens and doesn't rush you.

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November 11, 2025

5.0

As above very thorough

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November 11, 2025

5.0

Same as above. Thorough, friendly and always has time to answer any questions

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November 10, 2025

5.0

knowlegeable

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November 08, 2025

5.0

Dr. Bayer is very thorough, honest and to the point. He works with me and is knowledgeable of the best medications/plan for me.

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November 07, 2025

5.0

He was very helpful and thorough. He helped me to understand a test that I'd taken, that is, the results.

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November 07, 2025

5.0

He is a no nonsense doctor and understood my problem and solved it much to my satisfaction.

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November 05, 2025

5.0

The best!

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October 30, 2025

5.0

Takes time with his patients and explains everything.

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October 28, 2025

5.0

Dr. Bayer is a very knowledgeable and kind doctor

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October 28, 2025

5.0

He is last fantastic, extraordinary and perfect

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October 27, 2025

5.0

Great doctor...

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October 27, 2025

5.0

Very capable and trustworthy

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October 24, 2025

5.0

He's one of the best endocrinologists! His care is above and beyond. Love him!

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October 24, 2025

5.0

Absolutely the best doctor I have ever had. Listens and answers every question and gives you reasons for every recommendation.

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October 24, 2025

5.0

He is a great doctor who listens to you and does not make generalities on your specific medical issues

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October 22, 2025

5.0

Kind and capable

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October 21, 2025

5.0

Dr. Bayer has been my Doctor for over 25 years and he has always been very thorough and easy to talk to and I think my results speak for themselves.

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October 19, 2025

5.0

Dr. Bayer answers all my questions and is very polite and takes his work seriously in order to help take care of myself better.

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October 18, 2025

5.0

KNOWLEGABLE

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October 15, 2025

5.0

Dr Bayer is an asset to his patients and to Northwestern. Caring, knowledgable understanding and always takes time to listen. Thank you Dr Bayer!

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October 14, 2025

5.0

Highly recommend

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October 13, 2025

5.0

He is experienced, intelligent, kind, patient and has a wonderful sense of humor.

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October 08, 2025

5.0

He allows me to put in my input for treatment and medication

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September 28, 2025

5.0

Very caring and professional.

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September 24, 2025

5.0

Very relatable and he comes across as caring

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September 22, 2025

5.0

Dr Bayer goes way beyond the obvious symptoms and he is so very intelligent. He really cares about what his patient is going to experience once they leave the office.

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September 17, 2025

5.0

Dr bayer was lowered my A1C and heard me out on all my concerns. He's funny and super nice.

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September 12, 2025

5.0

Was very approachable and knowledgeable

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September 10, 2025

5.0

Professional

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September 10, 2025

4.0

Very attentive

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September 08, 2025

4.0

Knows what he is doing

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September 08, 2025

5.0

Dr. Bayer doesn't rush his patients, he takes the time to listen to any concerns I have.

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September 04, 2025

5.0

Very knowledgeable about diabetes and my needs

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September 02, 2025

5.0

All of my concerns and questions were answered.

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August 28, 2025

5.0

Dr Bayer makes me feel very comfortable and is very efficient. Great bedside manner

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August 26, 2025

5.0

He is a excellent in dealing with his patients, very friendly and kind

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August 21, 2025

5.0

I've been his patient for over 20 years and he has done a super job in caring for my health.

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August 21, 2025

5.0

My son has Learning Disability's and Doctor Bayer understands and makes him feel very comfortable.

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August 20, 2025

5.0

Very knowledgeable!

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August 12, 2025

5.0

Dr Bayer is an excellent doctor who combines a bit of humor with incredible knowledge. No questions is silly - he listens attentively and offers insight that a regular person can understand.

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August 07, 2025

5.0

He is very caring.

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August 06, 2025

5.0

Dr. Bayer has a great bedside manner. You can tell he really cares about his patients.

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August 05, 2025

5.0

Personable and knowledgeable

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August 04, 2025

5.0

Dr Bayer has a great bed side manner. He listens to what you have to say. Doesn't blow off concerns you might have. Stays on top of what tests you might need.

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July 31, 2025

5.0

He is kind, clearly spoken, gives reasonable and understandable explanations.

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July 30, 2025

5.0

He is very knowledgeable

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Disclosures

William C. Bayer, MD reported no external professional relationships for calendar year 2024.

External Professional Relationships

Pharmaceutical, device, and biotechnology companies frequently collaborate with basic scientists and physicians within an academic medical center to help advance science and improve patient care. These relationships are important in achieving scientific breakthroughs and in establishing the effectiveness and safety of promising new therapies. In order to assure objectivity in clinical research and patient care, the Northwestern University Feinberg School of Medicine (Feinberg), Northwestern Memorial HealthCare, Children's Hospital of Chicago Medical Center, and the Shirley Ryan AbilityLab have adopted integrity policies that require research and clinical faculty (in full-time, part-time, and unpaid/voluntary categories) to report compensated and uncompensated external industry relationships. Patients are encouraged to discuss these disclosures with their physician as well as to inquire as to how these relationships are overseen by Feinberg. To learn more about our Disclosure and Professional Integrity Policy, and the conflict of interest policies of our joint affiliate survey partners, please go to our Office for Regulatory Affairs Policies page.

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