What causes random bruises on legs?

Random or unexplained bruises on the legs are often caused by minor bumps or pressure that you may not notice, because bruises form when small blood vessels near the skin’s surface break and blood leaks into the surrounding tissue.

Common causes include:

• Unnoticed minor trauma, like bumping into furniture or a car door
• Aging, which can make skin thinner and blood vessels more fragile
• Intense exercise or repeated impact
• Medications that affect clotting, such as aspirin, ibuprofen/naproxen, or prescription blood thinners
• Some supplements, like fish oil or ginkgo, which may increase bruising in some people
• Heavy alcohol use, which can make bruising more likely in some people
• Less commonly, vitamin deficiencies or medical conditions that affect clotting or platelets, including liver disease or kidney disease

See a healthcare professional if bruises are frequent, very large, painful, appear without any clear reason, or come with other bleeding such as nosebleeds or bleeding gums.