Random bruising usually comes from minor bumps you don’t notice or remember, but when bruises appear frequently or without any clear cause, the explanation typically involves one of a few common factors: medications that affect clotting, age-related skin changes, nutritional gaps, or less commonly, an underlying bleeding disorder. Most cases turn out to be benign, but the pattern and location of your bruises can tell you a lot about whether something deeper is going on.
How Bruises Actually Form
A bruise is blood that has escaped from ruptured capillaries and small veins and spread into surrounding tissue. When something presses against your skin, the soft tissue underneath gets compressed and stretches outward. The tiny blood vessels embedded in that tissue get pulled straight, stretched along their length, and eventually tear. Red blood cells leak out and pool beneath the skin, creating the familiar discoloration.
This process doesn’t require a hard hit. Even light pressure against a table edge or bumping into a doorframe can rupture fragile capillaries, especially if other factors have made your blood vessels or skin more vulnerable. The blood doesn’t just stay right at the impact site either. It can travel into deeper tissue layers where muscle is compressed against bone, which is why a bruise sometimes appears slightly away from where the actual contact happened.
Medications That Increase Bruising
The most common reason for unexplained bruising in otherwise healthy adults is medication. Several widely used drugs reduce your blood’s ability to clot, meaning even tiny vessel tears that would normally seal quickly instead leak enough blood to leave a visible mark.
Over-the-counter pain relievers are frequent culprits. Aspirin, ibuprofen (Advil, Motrin), and naproxen (Aleve) all interfere with platelet function, the first step in forming a clot. If you take any of these regularly, you’re more likely to bruise from everyday contact you wouldn’t otherwise notice.
Prescription blood thinners carry a stronger effect. Warfarin, apixaban (Eliquis), rivaroxaban (Xarelto), and similar anticoagulants significantly slow clotting. Anti-platelet drugs like clopidogrel (Plavix) work differently but produce a similar outcome. Some antibiotics and antidepressants, particularly SSRIs, can also impair clotting as a side effect that patients don’t always connect to their bruising.
Corticosteroids, whether taken as pills or applied as creams over long periods, thin the skin itself rather than affecting clotting. Thinner skin means less cushioning over blood vessels, so bruises form more easily and tend to look more dramatic.
How Aging Changes Your Skin
If you’re over 50 and noticing more bruises on your forearms and hands, the most likely explanation is structural changes in your skin. With age, your dermis (the thick middle layer of skin) loses volume. The collagen and elastin fibers that give skin its strength break down faster and rebuild more slowly. A key moisture-retaining molecule in skin also diminishes, leaving tissue less resilient. In older skin, the dermis can thin to roughly half its normal thickness, dropping from about 1.4 to 1.5 millimeters down to 0.7 to 0.8 millimeters.
This thinning removes the protective cushion around capillaries. Minor contact that wouldn’t have left a mark at age 30 can now rupture vessels easily. The resulting bruises, sometimes called senile or actinic purpura, typically show up as flat, dark purple patches on the forearms and backs of the hands. They resolve over one to three weeks but often leave behind a faint brownish-yellow stain from iron deposits in the skin. Sun damage accelerates this process, which is why it tends to affect sun-exposed areas most.
The subcutaneous fat layer beneath the skin also thins with age, removing another buffer between the outside world and your blood vessels. In severe cases, a condition called dermatoporosis can develop, where the skin becomes so fragile that even routine activities cause extensive bruising or bleeding into deeper tissue layers.
Vitamin Deficiencies
Two nutrients play direct roles in preventing bruises, and being low in either one can make bruising noticeably worse.
Vitamin C is essential for building collagen, the structural protein that reinforces blood vessel walls. When vitamin C levels drop too low, collagen production falters and capillary walls weaken. The increased bleeding tendency in vitamin C deficiency comes from the breakdown of connective tissue around blood vessels rather than a problem with clotting itself. Full-blown scurvy is rare in developed countries, but mild vitamin C deficiency is more common than most people realize, particularly in smokers, people with very limited diets, and older adults.
Vitamin K is needed for your liver to produce several clotting factors. Without enough of it, even small vessel tears take longer to seal. Vitamin K deficiency is less common in adults since gut bacteria produce some of it, but it can develop in people taking long courses of antibiotics, those with digestive conditions that impair fat absorption, or people with very low dietary intake of leafy greens.
Bleeding Disorders
When bruising is truly frequent and disproportionate to any contact, a bleeding disorder may be responsible. The most common one is von Willebrand disease (VWD), which affects up to 1 in 100 people in the United States, roughly 3.2 million individuals. Many of them go undiagnosed for years because the symptoms can seem like just “easy bruising.”
VWD involves a deficiency or dysfunction of a protein that helps platelets stick together and form clots. People with VWD tend to bruise with very little or no apparent injury, bruise often (one to four times per month), get bruises larger than a quarter, and sometimes notice raised lumps beneath the bruised skin. Other signs include frequent nosebleeds, heavy menstrual periods, and prolonged bleeding after dental work or surgery.
Other bleeding disorders, including platelet function defects and rare clotting factor deficiencies, can also present as unexplained bruising. Some connective tissue disorders like Ehlers-Danlos syndrome make blood vessels more fragile and bruise-prone as well. A family history of similar symptoms is an important clue.
What the Pattern of Bruising Tells You
Not all bruising patterns carry the same significance. Bruises on the shins, forearms, and outer thighs are the most common and least concerning. These are high-contact areas where you’re likely bumping into things without registering it.
Bruises in certain locations warrant more attention. Bruising on the torso (chest, back, abdomen), neck, ears, or buttocks is less likely to come from accidental bumps and more likely to signal a clotting problem or other medical issue. The same goes for bruises that are unusually large, appear in clusters, or show up with a palpable lump underneath.
Other red flags include bruising accompanied by joint swelling after minor injury, bleeding gums, blood in urine or stool, or prolonged bleeding from small cuts. If you’re noticing these alongside your bruises, or if bruising started suddenly after beginning a new medication, those patterns help point toward a specific cause.
How Doctors Evaluate Unexplained Bruising
If your bruising is frequent enough to concern you, the initial evaluation is straightforward. A doctor will ask about your personal and family history of bleeding, what medications and supplements you take, and whether you’ve noticed other bleeding symptoms. They’ll also examine existing bruises for size, location, and whether they’re raised.
The standard first round of blood work includes a complete blood count to check your platelet levels, clotting time tests, fibrinogen measurement, and screening for von Willebrand disease. These tests cover the most common causes and usually provide an answer or at least narrow the possibilities.
If those initial tests come back normal but your bleeding symptoms are clearly abnormal, your doctor may order more specialized tests looking at individual clotting factors or platelet function. In some cases, the diagnosis ends up being what hematologists call a “bleeding disorder of unknown cause,” where standardized testing doesn’t identify a specific defect despite a real pattern of abnormal bleeding. This is a recognized diagnosis, not a dead end, and it still guides management decisions.