Why You Wake Up with Bruises You Don’t Remember Getting

Waking up to find a bruise you don’t recall earning can be unsettling—and it’s surprisingly common, especially among women. Bruises form when tiny blood vessels beneath the skin break and leak blood into surrounding tissue, creating marks that change color as they heal. In most cases, these bruises are harmless, but understanding why they appear can help ease concern and highlight when it’s time to look deeper.

Thinner or Sun-Damaged Skin

As skin ages—or experiences repeated sun exposure—it naturally becomes thinner and loses some of its protective fat and elasticity. This makes the small capillaries near the skin’s surface more vulnerable. Even minor pressure can cause them to rupture, leading to bruises you never noticed forming. These marks often appear on the forearms and hands and tend to be more noticeable in people with lighter or more fragile skin.

Minor Bumps You Didn’t Notice

One of the most common explanations is simple, unnoticed trauma. You may bump into furniture, door frames, or even your own limbs during daily activities or while sleeping—without realizing it. If your blood vessels are sensitive, even these small impacts can leave a bruise behind.

Iron Deficiency and Menstrual Blood Loss

Women of reproductive age are more prone to iron deficiency due to monthly menstrual blood loss. Low iron levels can weaken blood vessel walls and affect the body’s ability to clot properly, making bruising more likely. If unexplained bruises appear alongside fatigue, dizziness, or heavier-than-usual periods, it may be worth discussing iron levels with a healthcare provider.

Genetics and Individual Sensitivity

Some people are simply more prone to bruising due to genetics. If easy bruising runs in your family, you may share connective tissue traits that make capillaries more fragile. Hormonal fluctuations—such as those related to the menstrual cycle—can also temporarily increase bruise risk.

Vitamin Deficiencies That Affect Bruising

Certain nutrients play a key role in keeping blood vessels strong and clotting mechanisms healthy:

• Vitamin C supports collagen production, helping reinforce vessel walls
• Vitamin K is essential for proper blood clotting
• Vitamin B12 supports healthy blood cell production

Deficiencies in any of these can make bruising more frequent or appear without a clear cause.

Medications and Supplements

Some medications and supplements can increase bruising by thinning the blood or affecting clotting. Common examples include:

• Aspirin and other blood thinners
• NSAIDs such as ibuprofen or naproxen
• Corticosteroids
• Certain antidepressants
• Herbal supplements like ginkgo or high-dose fish oil

If bruising increases after starting a new medication or supplement, it’s worth mentioning to your doctor.

When Bruising May Signal Something More Serious

Most random bruises fade within a couple of weeks and aren’t cause for concern. However, you should seek medical advice if you notice:

• Large or frequent bruises appearing regularly
• Bruises that don’t heal or continue to grow
• Additional symptoms such as bleeding gums, extreme fatigue, night sweats, or unexplained weight loss

These signs may point to an underlying issue affecting blood clotting or blood cell production, such as a clotting disorder, liver condition, or—rarely—a blood-related illness.

Final Thoughts

Unexplained bruises can result from many everyday factors, including minor bumps, nutritional deficiencies, genetics, or medication effects. While most cases are benign, paying attention to patterns and accompanying symptoms is important. If something feels unusual, a simple conversation with a healthcare provider—and possibly a routine blood test—can offer clarity and peace of mind.