You bruise from minor bumps. Your genes may be the reason.

Factor V is a protein your body produces to start the clotting cascade. It’s like the spark that ignites the entire clotting process. When you get a cut or injury, Factor V activates other clotting factors in a precise sequence, and your blood forms a stable clot to stop the bleeding. This is a normal, protective process.

The Factor V Leiden variant (R506Q) makes your clotting factor harder to turn off. Approximately 5% of people with European ancestry carry this variant. Once your clotting cascade starts, it doesn’t stop as efficiently as it should. This means your blood forms clots more aggressively and keeps them intact longer. Even after the initial injury heals, your body keeps a partial clot around the damaged area, which is why bruises form so easily and persist.

You might notice that small bumps produce large, dark bruises that take much longer than normal to fade. You bruise from pressure that wouldn’t normally cause visible marks. In some cases, bruises appear without any obvious injury at all. If you’re on oral contraceptives, this risk increases dramatically because hormones amplify the clotting tendency.

Prothrombin is the precursor protein to thrombin, the molecule that actually converts fibrinogen into fibrin and creates the physical clot. Think of prothrombin as the factory that produces the clotting machinery. Higher prothrombin levels mean more raw material for clotting, and faster clot formation.

The G20210A variant in the F2 gene increases how much prothrombin your liver produces. This variant is carried by roughly 2-3% of people with European ancestry. You produce 20-30% more prothrombin than someone without this variant, which accelerates your entire clotting cascade. The effect is particularly strong when combined with other clotting variants like Factor V Leiden. Even without other variants, elevated prothrombin increases your clotting risk 2-3 fold.

You’ll notice that bruises develop quickly after even minor trauma. Small bumps cause disproportionately large bruises. You might also experience occasional swelling or a feeling of heaviness in your legs, especially after long periods of sitting or standing. Some people with this variant report that minor cuts take a very long time to stop bleeding once they finally start, because the clot becomes so stable.

MTHFR is the enzyme that converts folate and B12 into their active forms, which your body uses to regulate homocysteine. Homocysteine is an amino acid that, when elevated, damages blood vessel walls. Your body normally keeps homocysteine low by converting it into other molecules. MTHFR is a critical step in this conversion.

The C677T variant in MTHFR reduces the enzyme’s efficiency by 40-70%. Approximately 40% of people with European ancestry carry at least one copy of this variant. If you have this variant, your body struggles to convert folate and B12 into their active forms, and homocysteine builds up in your bloodstream. Elevated homocysteine directly damages the endothelium, the inner lining of your blood vessels, making them more fragile and more prone to bleeding and bruising.

You might notice that your bruises appear not just from trauma but also seem to form spontaneously. Your blood vessels feel weak and delicate. You may also experience fatigue, brain fog, or mood changes because this same inefficient enzyme affects your entire methylation cycle. Some people describe feeling like their skin is thin and easily damaged.

Plasminogen activator inhibitor-1 is a protein that slows down clot breakdown. After your blood forms a clot to stop bleeding, your body needs to gradually dissolve that clot as the wound heals. This is a balanced process: you need clots to form, but you also need them to dissolve at the right pace. PAI-1 controls how fast clot dissolution happens by inhibiting the enzymes that break down fibrin.

The 4G/5G polymorphism in PAI1 determines how much PAI-1 your body produces. People with the 4G/4G genotype, found in roughly 25% of the population, produce significantly more PAI-1. Higher PAI-1 levels mean clots dissolve more slowly, so bruises persist longer and accumulate more easily. This variant is particularly problematic because it doesn’t accelerate clotting formation, it just prevents clots from breaking down naturally. You end up with old clots still resorbing under your skin while new bruises are forming.

You’ll notice that bruises take an exceptionally long time to fade. A bruise from three weeks ago might still be visible when you get a new one. You may also experience occasional blood clots in your legs after flights or long periods of immobility. Some people report a sensation of heaviness or achiness in areas where bruises are healing.

Nitric oxide synthase 3 (endothelial NOS) is the enzyme that produces nitric oxide in your blood vessel walls. Nitric oxide is a signaling molecule that tells your blood vessels to relax and dilate, improving blood flow and protecting the endothelial lining. A healthy endothelium is smooth, intact, and resilient. It resists bruising because the vessels themselves are flexible and strong.

The Glu298Asp variant (rs1799983) in NOS3 reduces how much nitric oxide your blood vessels produce. Approximately 30-40% of people carry this variant. Lower nitric oxide production means your blood vessels stay slightly constricted, their walls become stiffer, and the endothelial lining becomes more fragile and prone to rupture. When blood vessels are fragile, even minor bumps cause them to leak blood into surrounding tissue, creating bruises.

You might notice that your bruises appear with almost no apparent cause, or from very light pressure. Your skin feels thin. You may also experience higher blood pressure than your peers, cold hands or feet, or a sensation that your circulation is sluggish. Some people report easy bruising combined with poor wound healing.

VKORC1 is the enzyme that recycles vitamin K so your body can use it repeatedly for clotting factor activation. Vitamin K is essential for making clotting factors 2, 7, 9, and 10. After your body uses vitamin K in the clotting cascade, VKORC1 reduces it back to its active form so it can be used again. This recycling process is extremely efficient normally, so dietary vitamin K is usually sufficient.

Certain variants in VKORC1 reduce the enzyme’s efficiency, meaning you recycle vitamin K more slowly and need higher dietary intake. Even people who eat adequate vitamin K can end up functionally deficient because their VKORC1 enzyme doesn’t recycle efficiently. When clotting factors are slightly depleted, blood vessels become more fragile and prone to bleeding. Bruises form more easily because your blood lacks sufficient clotting factor to seal vessel injuries quickly.

You might notice that your bruises appear in clusters or seem worse during times when your vitamin K intake is lower (winter months, periods of less vegetable intake). You may also experience prolonged bleeding from minor cuts or a feeling that small injuries take forever to stop bleeding. Some people report that bruises are accompanied by small red dots (petechiae) from capillary rupture.