Random bruises usually come from minor bumps you didn’t notice at the time, but when they keep appearing without any obvious injury, the cause is typically something affecting your blood’s ability to clot or your skin’s ability to protect the small blood vessels underneath it. Medications, nutritional gaps, aging, and certain medical conditions can all make you bruise more easily.
How Bruises Form
Underneath your skin sits a network of tiny blood vessels called capillaries. When something damages them, even light pressure you barely register, blood leaks into the surrounding tissue. Your body then breaks down that trapped blood over roughly two weeks, which is why a bruise shifts from pinkish-red to deep purple, then fades through green and yellow before disappearing entirely.
Some people have naturally fragile capillaries that rupture more easily, leading to what looks like spontaneous bruising. This capillary fragility can be inherited, or it can develop over time from medications, nutritional deficiencies, or changes in your skin and connective tissue.
Medications That Increase Bruising
This is one of the most common and most overlooked causes. Several widely used medications reduce your blood’s ability to form clots, which means even a tiny capillary break bleeds more than it normally would. The usual suspects include aspirin, ibuprofen, and naproxen. If you take a blood thinner like warfarin, rivaroxaban, or apixaban, easy bruising is an expected side effect, not a mystery.
Certain antidepressants and antibiotics can also interfere with clotting. Corticosteroids work differently: rather than changing your blood chemistry, they thin the skin itself, removing the cushion that normally protects capillaries from everyday contact. Even dietary supplements can play a role. Ginkgo biloba, for example, has a blood-thinning effect that raises bruising risk. Fish oil supplements do reduce platelet clumping in lab measurements, though a systematic review of 52 studies found this didn’t translate into meaningful bleeding problems in real-world settings.
If you recently started a new medication or supplement and noticed more bruises, that connection is worth exploring with your pharmacist or doctor.
Vitamin Deficiencies
Two vitamins play direct roles in keeping bruises at bay. Vitamin C is essential for building collagen, the protein that gives your blood vessel walls their structure and strength. Without enough of it, capillaries become fragile and leak more easily. Severe vitamin C deficiency (scurvy) causes widespread bruising, bleeding gums, and slow wound healing, but even a mild shortfall can make you bruise more than usual.
Vitamin K is the other key player. Your liver needs it to produce several clotting factors that stop bleeding after a vessel breaks. When vitamin K levels drop, those clotting proteins don’t work properly, and small bleeds under the skin take longer to seal off. Most people get enough vitamin K from leafy greens, but poor dietary variety, certain digestive conditions that impair fat absorption, or prolonged antibiotic use can create a deficit.
Aging and Skin Changes
If you’re over 50 and noticing bruises on your forearms and hands, you’re likely seeing something called senile purpura. It’s extremely common and not dangerous, though it can look alarming. Years of sun exposure break down collagen and elastin in the skin, leaving it thinner and less padded. Research published in the Annals of Dermatology confirmed that people with this condition have measurably thinner skin than those without it.
The result is that capillaries sit closer to the surface with less protection. A light knock against a doorframe or even firm pressure from a watch band can cause a bruise you never felt happen. These bruises tend to be flat, purple, and irregularly shaped, mostly appearing on sun-exposed areas like the backs of the hands and forearms.
Blood and Clotting Disorders
When bruising is frequent and truly unexplained, a bleeding disorder is sometimes responsible. The two most relevant conditions are low platelet counts and von Willebrand disease.
Low Platelet Count
Platelets are the cells that rush to a damaged blood vessel and form the initial plug that stops bleeding. A healthy adult has between 150,000 and 400,000 platelets per microliter of blood. When that number drops significantly, a condition called thrombocytopenia, bruises appear more easily and take longer to resolve. Causes range from viral infections and autoimmune conditions to bone marrow problems and certain medications.
Von Willebrand Disease
This is the most common inherited bleeding disorder. It involves a protein that helps platelets stick together and to damaged vessel walls. People with von Willebrand disease often bruise easily from childhood and may also experience frequent nosebleeds, heavy menstrual periods, prolonged bleeding from minor cuts, and excessive bleeding after dental work. A simple blood test measuring the levels and function of the von Willebrand factor protein can confirm or rule out the diagnosis.
Liver Disease
Your liver manufactures most of the proteins your blood needs to clot. When the liver is damaged, whether from chronic alcohol use, hepatitis, fatty liver disease, or cirrhosis, its production of clotting factors drops. This includes the vitamin K-dependent factors as well as other clotting proteins, anticoagulant proteins, and thrombopoietin, which regulates platelet production. Advanced liver disease can also cause the spleen to enlarge and trap platelets, reducing circulating levels even further.
Easy bruising from liver disease rarely appears in isolation. It usually comes alongside other signs like fatigue, yellowing of the skin or eyes, swelling in the legs or abdomen, or spider-like blood vessels on the chest and face.
Other Contributing Factors
A few additional causes are worth knowing about. Intense exercise, particularly heavy weightlifting or contact sports, can produce bruises from micro-trauma to muscles and skin you may not feel during the activity. Alcohol thins the blood and impairs liver function even before liver disease develops, so heavy drinking can increase bruising on its own. Women tend to bruise more easily than men due to differences in skin thickness and fat distribution. And genetics simply make some people more prone to visible bruising than others, with no underlying disease involved.
Signs That Deserve Attention
Most unexplained bruises are harmless and heal completely within two weeks. But certain patterns suggest something more than everyday fragility. Cleveland Clinic recommends seeing a healthcare provider if a bruise doesn’t improve after a week, is unusually large or painful, keeps reappearing in the same spot, shows up without any clear cause, or appears in areas unlikely to be bumped, like your back, torso, or abdomen.
Bruises accompanied by other bleeding symptoms, such as frequent nosebleeds, blood in your urine or stool, or gums that bleed when you brush your teeth, are a stronger signal that something systemic is going on. A basic blood test checking your platelet count and clotting function can quickly narrow down or rule out the more serious possibilities.