Waking up with bruises you don’t remember getting is surprisingly common, and in most cases it comes down to bumping into things during the night without noticing, combined with factors that make your skin bruise more easily. A bruise forms when small blood vessels beneath the skin break and leak blood into surrounding tissue. The real question isn’t usually whether you bumped something, but why your body seems to bruise from such minor impacts that you don’t even recall them.
Medications That Make You Bruise Easily
This is the most frequently overlooked cause. Several everyday medications reduce your blood’s ability to clot, which means even light contact with a nightstand, bed frame, or your own knee can leave a visible mark by morning. The biggest culprits include blood thinners, NSAIDs like aspirin and ibuprofen, and steroids such as prednisone. If you take a daily aspirin for heart health and also pop ibuprofen for a sore back, the combination amplifies your bruising risk beyond what either would cause alone.
SSRIs, a common class of antidepressants, also interfere with platelet function and can increase bruising. Cancer medications are another well-known cause. If you’ve recently started or changed any medication and noticed more unexplained bruises, the timing probably isn’t a coincidence.
Supplements You Might Not Suspect
Certain herbal supplements thin the blood in ways that mimic medications. Garlic supplements inhibit platelet clumping, and case reports have linked high-dose garlic products to spontaneous bleeding events. Ginkgo biloba works through a similar mechanism, blocking a molecule that helps platelets bind together. When either supplement is taken alongside aspirin or ibuprofen, the bleeding risk increases further. One case described spontaneous eye bleeding in a man taking both ginkgo and aspirin.
Fish oil, vitamin E, and turmeric are other common supplements associated with easier bruising. Because these are sold over the counter and marketed as natural, many people don’t think to mention them when wondering why bruises keep appearing.
Nutritional Deficiencies
Your blood vessels depend on certain nutrients to stay intact. Vitamin C is essential for collagen production, and collagen is the structural protein that keeps capillary walls strong. When vitamin C levels drop low enough, those walls weaken and break under minimal pressure. The resulting bruises tend to appear on the legs, especially around hair follicles. A clinical case documented extensive bruising in a patient whose vitamin C level had fallen below 5 micromoles per liter, well under the normal range of 40 to 100. You don’t need to have full-blown scurvy for this to matter; even moderately low levels can increase capillary fragility.
Vitamin K plays a different but equally important role: it helps your blood form clots. Without enough of it, even tiny vessel breaks take longer to seal, and blood pools beneath the skin. People who eat very few green vegetables or who have conditions affecting fat absorption are most at risk for low vitamin K.
Skin Changes With Age
If you’re over 60, the answer may be partly structural. A condition called senile purpura (also known as actinic purpura) causes dark, flat bruises on sun-exposed skin, particularly the forearms and hands. It affects roughly 10% of older adults, with an average onset around age 71. Years of sun exposure break down the connective tissue that cushions blood vessels, and the skin itself becomes measurably thinner. The result is that everyday contact, like resting your arm against a table edge while you sleep, can produce a bruise that would never have appeared at age 30.
This isn’t dangerous, but it is worth distinguishing from other causes. Senile purpura bruises typically show up on the outer surfaces of the forearms and backs of the hands rather than on the torso or inner limbs.
Moving in Your Sleep
Some people physically act out dreams or move aggressively during sleep without any awareness. In a clinical study of 45 parasomnia patients, 69% had sleepwalking and injuries ranged from breaking objects (25% of sleepwalkers) to shoulder dislocations. Dangerous sleep behaviors were nearly five times more common in younger adults and in men, and alcohol use increased parasomnia events dramatically, with a 21-fold higher association in males compared to females.
REM sleep behavior disorder is a related condition where the normal muscle paralysis during dreaming doesn’t engage properly. People with this disorder punch, kick, or thrash, sometimes injuring themselves or a bed partner. If you wake with bruises and your partner reports that you move violently in your sleep, or if you’ve ever woken up on the floor or in an unexpected position, a sleep disorder is worth investigating.
Bleeding Disorders and Other Medical Conditions
Less commonly, unexplained bruising signals an underlying problem with how your blood clots. Von Willebrand disease is the most common inherited bleeding disorder, and many people with mild forms don’t get diagnosed until adulthood, when they start noticing easy bruising, heavy periods, or prolonged bleeding from cuts. Hemophilia is rarer but follows a similar pattern of excessive bruising.
Low platelet counts, a condition called thrombocytopenia, can result from autoimmune diseases, certain infections, or bone marrow problems including leukemia. Liver disease also impairs clotting because the liver produces most of the proteins your blood needs to stop bleeding. Connective tissue disorders like Ehlers-Danlos syndrome cause bruising through a completely different path: the collagen supporting blood vessel walls is structurally defective, making capillaries and even larger vessels fragile enough to leak from minimal force.
Patterns That Deserve Attention
Most unexplained bruises are harmless, but certain characteristics suggest something more serious is going on. Be alert to bruises that are unusually large or numerous, bruises on the torso, neck, ears, or buttocks (areas that don’t typically bump into things), and bruises that appear in clusters or form recognizable patterns. Multiple bruises at different stages of healing appearing simultaneously, or bruises accompanied by frequent nosebleeds, bleeding gums, or blood in your urine, point toward a systemic clotting problem rather than simple nighttime bumps.
If a doctor suspects a bleeding disorder, the initial workup typically involves a complete blood count to check platelet levels and clotting time tests. Normal clotting times paired with easy bruising often point toward von Willebrand disease. Abnormal results in both major clotting tests can indicate liver problems or a more complex coagulation issue.
How Bruises Heal
A normal bruise progresses through a predictable color sequence as your body breaks down the trapped blood. It starts pinkish-red, shifts to dark blue or purple within a day or two, then fades through violet and green before turning dark yellow and finally pale yellow. The whole process typically takes about two weeks. If your bruises consistently take much longer than that to resolve, or if they seem to expand rather than fade over the first few days, that’s another signal that your clotting system may not be working as expected.