If you have more than 11 moles on your right arm, you’re at increased risk for melanoma, the deadliest form of skin cancer, finds a new study. It means that you likely have more than 100 moles over your entire body, a known risk factor.

The arm check is a quick way to see if you need further screening. If your count is high, schedule regular full-body exams with a dermatologist. Early detection is a lifesaver when it comes to melanoma.

Got fewer moles? You’re not off the hook! Not all melanomas emerge from existing moles. It’s important to know what’s normal for your skin and to let your doctor know if you see any change in the size, shape, color or feel of a mole—or any other patch of skin.

To learn more, see Bottom Line’s Guide to Skin Cancer: Prevention, Detection and Treatment and Bottom Line’s article Deadly Melanoma: Best Prevention, Detection and Treatment Breakthroughs.