The Times wants to hear from patients and providers about medical practices affiliated with Optum, a subsidiary of UnitedHealth Group. Share your experience below.

Health care in America is changing. The days of small, independent medical practices have mostly passed. Today, most doctors work for a large corporation. Acquisition sprees by hospitals, health systems, private equity firms and health insurers have given a relatively small number of companies outsize control over a $4.5 trillion industry with extraordinary consequences for people’s daily lives.

Amid this wave of consolidation, one company stands apart. UnitedHealth Group, which owns the nation’s largest insurer, also employs or is affiliated with roughly 90,000 doctors — more than any other company. Through its lesser-known subsidiary Optum, it operates primary care practices, specialty clinics, home health agencies, urgent care centers and other facilities across the country.

This combination is at the core of the company’s growth strategy and has led to record profits. The Times wants to understand what it has meant for Optum’s patients and medical professionals. We’d especially like to know about any changes that occur when Optum buys or contracts with a medical practice.

Step 1: Unsure whether Optum owns or contracts with your clinic? Click here to see a state-by-state list of Optum-affiliated practices. (Note: This list is not exhaustive.)

Step 2: If you are a medical professional who has worked at an Optum-affiliated practice, if you are a patient at one, or if you have something else to share, please fill out the questionnaire below. (You’ll see provider questions first, then questions for patients.)

Step 3: Share the link to this questionnaire within your networks so we can hear from more people.

A Times reporter may reach out to you to learn more about your story. We will not share your contact information outside the Times newsroom or use it for any reason other than to get in touch with you. And we will not publish any part of your response without verifying your information and hearing back from you. If you prefer to share your story anonymously, you can do so through our tips page.