When your doctor orders a test for you, it’s important to know what type of test is ordered. There are two types, preventive and diagnostic.

Knowing the difference between these two types of tests will help you better understand your treatment plan. It will also help you understand how your health plan will pay for it. 

What’s the Difference?

A screening test is often part of preventive care. Preventive screenings are routine tests ordered when there is no reason to suspect a problem. They are usually done at certain ages or timeframes depending on what they are for. The goal of these screenings is to check your health status and keep you healthy.

A diagnostic test is ordered when there are signs or symptoms of a possible problem. Diagnostic tests may also be ordered when anything unusual shows up on a preventive screening test. These tests take a closer look to see if disease is present. They are used to confirm or rule out a cause of the symptoms.

Screening tests, such as Pap smears, colonoscopies and mammograms, are often less invasive than diagnostic tests, such as a biopsy.

But some types of tests may have both preventive and diagnostic versions. For example, colonoscopies and mammograms have both screening and diagnostic versions.

A colonoscopy is often done as a preventive measure to detect any early signs of colon or rectal cancer. But a colonoscopy can also be a diagnostic test if it’s done because a problem is suspected or if previous screening colonoscopies showed polyps or other issues.

Similarly, a screening mammogram is usually performed regularly as a preventive measure. It’s used to detect breast cancer early, often before a lump can be felt. Your doctor may request a diagnostic mammogram if needed to check any suspicious breast changes or signs of a problem discovered from a screening test. 

Test Type and Your Cost Share

Many health plans cover most preventive health care services with no out-of-pocket costs.* This coverage applies when you go to your primary care provider or medical group (for HMOs) or a doctor or medical center in your plan’s network (for non-HMO plans).

That means you pay no copay or coinsurance even if you haven’t met your deductible. You can find details about the preventive services your plan covers in your benefit materials.

A diagnostic test is considered medical care, not preventive care. You may have out-of-pocket costs for these types of tests. The costs depend on what your doctor orders and if there are other requirements for that kind of test. For example, some states have laws that require certain tests to be covered without cost.

Get the Details on Your Costs

To avoid unexpected out-of-pocket costs, here are some questions to ask your care team:

• What type of test or procedure will be ordered?
• Is it covered by my health plan?
• Is the provider in-network? Will any other providers be involved in the tests or procedures? Are they also in-network? Is the facility in-network?
• Are there any other related services or fees that may affect my costs?

To make sure a provider or facility is in your plan’s network, log in to Blue Access for Members^SM and go to Find Care in the My Health section. Then select Find a Doctor or Hospital to search for the provider and location that is right for you. Depending on your plan, you may also be able to estimate the out-of-pocket costs for your tests or treatments.

Knowledge is power. Know what type of test you’ll receive. This is the best way to be prepared to ask questions and not be surprised by unplanned costs.

*If you have a grandfathered plan (a plan that started on or before March 23, 2010), preventive care without out-of-pocket costs may not apply to you.

Sources: Screening and Diagnostic Tests: Know the Difference,  Labcorp; Preventive vs. diagnostic care: What to know and why it matters,  UCLA Health, 2022; Diagnostic Mammogram,  National Breast Cancer Foundation, 2025