Bruising happens when an impact crushes small blood vessels beneath the skin without breaking it open. Those vessels leak blood into the surrounding tissue, creating the familiar discoloration that starts reddish, shifts to bluish-purple, then fades to greenish-yellow before disappearing. Most bruises are harmless and heal on their own within two weeks, but unexplained or frequent bruising can signal something deeper, from medications and nutritional gaps to blood disorders and organ disease.
Physical Trauma and Everyday Injuries
The most straightforward cause is a bump, fall, or knock against something hard. The force ruptures tiny blood vessels called capillaries, and leaked blood pools under the skin. People who are physically active, play contact sports, or work manual jobs tend to bruise more often simply because of more frequent impacts. These bruises are rarely a concern and typically resolve in about two weeks, though larger ones can linger for a month or longer.
Aging and Skin Changes
If you notice bruises appearing more easily as you get older, your skin is largely to blame. With age, the connective tissue in the deeper layers of skin thins out, subcutaneous fat decreases, and the structures anchoring skin layers together flatten. The result: blood vessels lose the cushioning that once protected them, so even minor bumps can cause them to rupture. Sun-damaged skin is especially vulnerable. Years of UV exposure accelerate collagen breakdown, which is why the dark, blotchy bruises common in older adults tend to cluster on the forearms and backs of the hands, areas with the most cumulative sun exposure.
Medications That Increase Bruising
Several common medications reduce your blood’s ability to clot, making bruises more likely and longer-lasting. The main culprits include:
- Blood thinners (anticoagulants), which directly interfere with the clotting process. Combining a blood thinner with an over-the-counter pain reliever raises the risk further.
- NSAIDs like aspirin and ibuprofen, which reduce the clumping ability of platelets, the tiny cell fragments responsible for plugging damaged vessels.
- Steroids such as prednisone, which thin the skin over time and weaken blood vessel walls.
- Chemotherapy drugs, which can suppress the bone marrow’s ability to produce enough platelets.
If you started a new medication and noticed more bruising shortly after, the drug is a likely explanation. Don’t stop taking a prescribed medication on your own, but it’s worth flagging the change with whoever prescribed it.
Nutritional Deficiencies
Two vitamins play direct roles in preventing bruises. Vitamin K is essential for producing the clotting factors your blood needs to seal off damaged vessels. Without enough of it, those clotting factors are underproduced or don’t function properly, and bleeding under the skin becomes more common. Most people get adequate vitamin K from leafy greens, but conditions that impair fat absorption (since vitamin K is fat-soluble) can lead to deficiency even with a decent diet.
Vitamin C supports the structural integrity of blood vessel walls by helping build collagen. Severe deficiency, historically known as scurvy, causes widespread bruising along with bleeding gums and slow wound healing. True scurvy is rare in developed countries, but marginal vitamin C intake, especially in people with very limited diets, can still weaken vessels enough to bruise easily.
Liver Disease
The liver manufactures most of the proteins your blood relies on to clot. When the liver is damaged, whether from chronic alcohol use, hepatitis, fatty liver disease, or cirrhosis, production of these clotting proteins drops. The liver also produces a hormone that regulates platelet production and helps recycle vitamin K. Liver disease disrupts all of these functions simultaneously, creating a compounding effect where clotting slows down from multiple directions at once. Easy bruising is one of the earlier visible signs of significant liver dysfunction, often appearing alongside fatigue, swelling in the legs, or yellowing of the skin.
Low Platelet Count
Platelets are the first responders when a blood vessel breaks. They rush to the injury site and clump together to form a temporary plug. A normal platelet count falls between 150,000 and 450,000 per microliter of blood. Dropping below 150,000, a condition called thrombocytopenia, increases the risk of easy bruising along with other bleeding symptoms like nosebleeds or bleeding gums.
Platelet counts can drop for many reasons: viral infections, autoimmune conditions where the body destroys its own platelets, bone marrow disorders, or as a side effect of certain medications. The lower the count, the more easily bruises form and the larger they tend to be.
Von Willebrand Disease and Bleeding Disorders
Von Willebrand disease is the most common inherited bleeding disorder, and many people who have it don’t realize it until they notice a pattern of unusual bruising. According to the CDC, the bruising pattern that suggests a bleeding disorder has some specific features: bruises that appear with very little or no injury, occur one to four times per month, are larger than a quarter, and feel raised rather than flat.
Diagnosis involves blood tests that measure how well clotting proteins are working. Because many medications can mimic bleeding disorder symptoms, doctors will typically ask about any drugs you take before running these tests. A family history of heavy bleeding, whether from nosebleeds, dental procedures, or menstrual periods, is another strong indicator.
When a Bruise Needs Attention
Most bruises heal without any intervention, but some features suggest something more serious. A hematoma, which is a larger, raised collection of blood that feels painful to the touch, may need medical evaluation. These are distinct from ordinary flat bruises and indicate a greater volume of blood has escaped the vessels.
Bruises worth having checked include those that form a noticeable lump, appear on the abdomen or trunk without an obvious cause, keep growing in size after the first day or two, or are accompanied by other bleeding symptoms like blood in the urine or stool. Bruising that shows up in unusual locations, particularly around the eyes or on the torso without trauma, can occasionally indicate internal bleeding or a blood disorder that hasn’t been diagnosed yet.
Frequent, unexplained bruising that doesn’t match any of the common causes above, especially if it’s a new pattern, is worth investigating with a simple blood panel that checks platelet count, clotting time, and liver function.