Random bruising on your legs or body can be confusing. Most bruises come from minor injuries you simply don’t remember. But sometimes, unexplained bruising signals something deeper. As you age, skin becomes thinner and blood vessels weaken, making bruises appear more easily. Vitamin C and K deficiencies also play a role—C strengthens vessel walls, while K helps blood clot. Without enough of either, even light pressure can leave a mark.

Certain medications and supplements thin the blood. Aspirin, antibiotics, anticoagulants, even ginger and turmeric can make you bruise more easily. If you’re on blood thinners, a small knock can leave a large black-and-blue patch. Heredity matters too. If your parents bruised easily, you probably will. Women bruise more than men due to more fragile vessels. Most of the time, random bruising is harmless.

But sometimes it’s not. Bleeding disorders like hemophilia cause large, unexplained bruises along with nosebleeds and heavy bleeding from small cuts. Diabetes can damage blood vessels, leading to bruising that lasts longer and heals slowly. Liver and kidney disease, autoimmune conditions like lupus, and even viral infections such as chickenpox can affect clotting. Cancer treatments like chemotherapy also lower platelet counts, causing easy bruising.

When should you worry? See a doctor if bruises don’t heal within two weeks, appear suddenly with no cause, or come with severe pain, swelling, or signs of infection. Unexplained bruising alone isn’t usually a crisis. But when paired with other symptoms—fatigue, weight loss, fever, or bleeding gums—it’s worth checking out. Your body leaves clues. Sometimes a bruise is just a bruise. Sometimes it’s a quiet warning. The difference is knowing when to listen.