Excessive bruising usually comes down to one of a few things: your blood isn’t clotting properly, your blood vessels are too fragile, or something is interfering with the platelets that help seal off injuries. Sometimes it’s as simple as a medication side effect or a vitamin you’re low on. Other times, it points to an underlying condition worth investigating. Understanding the most common causes can help you figure out whether your bruising pattern is worth bringing up with a doctor.
How Bruising Works in Your Body
When you bump into something, tiny blood vessels beneath your skin can break open. Normally, your body stops the bleeding through a rapid chain of events: the damaged vessel tightens to slow blood flow, platelets rush to the site and clump together to form a temporary plug, and then a cascade of clotting proteins builds a more permanent seal. A bruise forms when blood leaks out before that process finishes, pooling under the skin and creating the familiar discoloration.
Anything that weakens a link in this chain can lead to bigger or more frequent bruises. Fragile blood vessels break more easily. Low platelet counts mean fewer cells available to plug the gap. And problems with clotting proteins mean the seal takes longer to form, allowing more blood to escape. Most causes of excessive bruising fall into one of these three categories.
Medications That Increase Bruising
This is the single most common explanation for new or worsening bruising. Several widely used medications reduce your blood’s ability to clot, either by thinning the blood directly or by interfering with platelet function. The most familiar culprits are aspirin and ibuprofen, both of which block platelets from clumping together effectively. Prescription blood thinners and antiplatelet drugs do this even more aggressively.
Corticosteroids, often prescribed for conditions like asthma, arthritis, or autoimmune diseases, cause bruising through a different mechanism. They thin the skin itself over time, making blood vessels closer to the surface and easier to damage. If you’ve been on a corticosteroid for weeks or months and notice bruises appearing with minimal contact, that’s a well-known side effect.
If you take any combination of these medications, the effect can stack. Someone on both a blood thinner and a daily aspirin, for instance, will bruise far more easily than someone on either one alone.
Supplements That Affect Clotting
Several popular supplements can increase bruising risk in ways people don’t expect. Garlic supplements inhibit platelet clumping through multiple pathways, and research shows they can amplify the blood-thinning effects of aspirin and similar drugs. Ginkgo biloba works similarly, blocking a compound called platelet-activating factor that helps platelets stick together. One case report documented spontaneous bleeding in a man’s eyes after he combined ginkgo with aspirin.
High-dose fish oil can also reduce platelet activity. If you’re taking any of these supplements alongside blood-thinning medication, the combination may explain bruises that seem to appear from nowhere.
Vitamin Deficiencies
Two vitamins play direct roles in preventing bruises. Vitamin C is essential for building collagen, the structural protein that reinforces your blood vessel walls. When vitamin C levels drop low enough, those walls weaken and capillaries begin to leak. The resulting bruising tends to show up around hair follicles and on the backs of the legs. Other signs of significant deficiency include fatigue, weakness, and brittle or corkscrew-shaped hairs. Full-blown scurvy is rare, but milder deficiency is more common than most people realize, especially in smokers and people with very limited diets.
Vitamin K is the other critical nutrient. Your liver needs it to manufacture several key clotting proteins. Without enough vitamin K, those proteins drop, and your blood takes longer to clot after any vessel damage. People with digestive conditions that impair fat absorption are at higher risk, since vitamin K is a fat-soluble vitamin.
Liver Disease
Your liver produces most of the proteins involved in blood clotting. When liver function declines, as in cirrhosis or advanced hepatitis, production of these clotting factors falls. Liver disease also impairs the body’s ability to use vitamin K, compounding the problem. The result is a measurable increase in clotting time and noticeably easier bruising.
Liver disease can also cause the spleen to enlarge, which traps and destroys platelets faster than normal, further reducing your body’s ability to stop bleeding. If excessive bruising is accompanied by yellowing skin, abdominal swelling, or dark urine, liver involvement is worth investigating.
Low Platelet Counts
A normal platelet count falls between 150,000 and 400,000 per microliter of blood. When counts drop below 50,000, bleeding risk increases even during routine daily activities. At very low levels, bruises can appear without any obvious injury at all.
Platelets can drop for many reasons. Viral infections, certain medications, autoimmune conditions, and bone marrow disorders can all suppress platelet production or accelerate their destruction. Heavy alcohol use is another common cause. If a blood test reveals low platelets, the next step is typically figuring out whether the problem is production, destruction, or both.
Von Willebrand Disease and Inherited Bleeding Disorders
Von Willebrand disease is the most common inherited bleeding disorder, affecting up to 1 in 100 people in the United States. Many people with mild forms don’t know they have it. The condition involves a deficiency or dysfunction of a protein that helps platelets stick to damaged vessel walls. Without it, the initial platelet plug forms poorly, and bruises come easily.
The CDC describes a specific bruising pattern associated with von Willebrand disease: bruises that occur with very little or no trauma, happen one to four times per month, are larger than a quarter, and are raised rather than flat. If that pattern sounds familiar, especially if you also have heavy periods, frequent nosebleeds, or prolonged bleeding after dental work, it’s worth asking about testing.
Hemophilia, which involves deficiencies in other clotting proteins, tends to cause deeper bleeding into joints and muscles rather than surface-level bruises. Large, swollen blue areas around joints, buttocks, or the neck after minor injuries are characteristic of these more severe clotting disorders.
Age and Sun Damage
If you’re over 60 and noticing more bruises on your forearms and hands, you’re likely experiencing a condition sometimes called senile purpura. Years of sun exposure gradually break down the connective tissue that supports blood vessels in the skin. At the same time, aging skin naturally becomes thinner and loses its fatty padding. The combination leaves blood vessels with less structural protection, so they break from everyday contact that wouldn’t have caused a bruise decades earlier.
These bruises are typically flat, purple-red, and concentrated on sun-exposed areas like the forearms and backs of the hands. They’re cosmetically annoying but not dangerous on their own. That said, new or worsening bruising in an older adult still deserves a basic blood workup to rule out other causes.
Where Bruises Appear Matters
Bruises on your shins, knees, and forearms are common spots for everyday bumps and usually don’t raise concern. What draws clinical attention is bruising in locations that don’t typically get bumped: the trunk, back, upper arms, and face. Bruises in these areas are more likely to suggest a systemic clotting problem rather than simple clumsiness.
The size and behavior of bruises also matter. Small, flat, pinpoint-sized dots (called petechiae) suggest a platelet problem. Larger, spreading bruises that feel raised or firm point more toward clotting factor deficiencies. Bruises that take weeks to resolve, or that appear in crops of different colors suggesting they formed at different times, are another pattern worth discussing with a healthcare provider.
Sorting Out What’s Normal
Almost everyone gets occasional bruises they can’t explain, especially on the legs. Women tend to bruise more easily than men, partly due to differences in skin thickness and fat distribution. A bruise here and there, particularly after physical activity, usually isn’t a sign of anything serious.
The pattern that warrants attention is a change from your baseline: bruising that’s noticeably more frequent, larger, slower to heal, or appearing in unusual locations. If bruising is accompanied by other bleeding symptoms like frequent nosebleeds, bleeding gums, blood in your urine or stool, or unusually heavy periods, the combination is more significant than any single symptom alone. A complete blood count, clotting time tests, and sometimes specific factor assays can usually identify or rule out the most common underlying causes.