Peeking at Your Genes Can Raise Red Flags for Life Insurers

If you have genetic mutations linked to breast cancer, Alzheimer’s, or dementia, there’s a chance you could be rejected for life and long-term care insurance.

Advocates of genetic testing worry that people will forgo testing—and therefore earlier identification and treatment of diseases—out of fear of losing coverage.

Companies such as 23andMe Inc. increasingly let people test for genetic markers that may foreshadow serious diseases later, which can be a boon for scientific research and patient care.

But ignorance may be bliss when it’s time to sign up for insurance. Employers and health insurers by law can’t discriminate on the basis ...