Bumps or protruding veins in your upper arms may be a sign of several harmful conditions; however, it could simply be the result of increased exercise. Most people's veins are flat under the skin, but a low body fat percentage can make the veins in your biceps stick out. A bump in one part of your vein or bicep is likely caused by a clot or a tear. See your doctor for a diagnosis.
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Superficial thrombophlebitis is a condition characterized by inflammation in your veins just under the surface of the skin; it can also mean there is a small blood clot in your veins. Superficial thrombophlebitis generally affects the legs, but veins in the arms and other areas may also be affected. Superficial thrombophlebitis is likely to only affect you for two to six weeks before it disappears on its own. However, it is possible that a blood cloth could move to a place where the affected superficial vein meets a larger, deep vein, causing a more serious condition called deep vein thrombosis.
Deep Vein Thrombosis
Deep vein thrombosis is characterized by a blood clot in one of your deep veins. This condition is more serious than superficial thrombophlebitis. Deep vein thrombosis may affect the veins in your arms, legs, intestines, liver, kidney or brain. The clots can block blood flow. Deep vein thrombosis in the biceps or other areas may be life threatening. Clots can kill you if one comes loose and travels to your lungs, where it can block blood flow and cause a pulmonary embolism. Clots in the legs may also cause complications that could lead to symptoms such as leg ulcers or swelling.
A bump or bruise on your biceps could indicate biceps tendinopathy. Repetitively using a tendon can lead to an injury, which is called tendinopathy. Using your biceps to bend your elbow can, over time, lead to biceps tendinopathy; overuse from too much exercise can also cause this condition. Biceps tendinopathy specifically refers to pain or even a tear in the biceps tendon, which connects at the shoulder and elbow. If the tendon ruptures, it may cause a pop, pain and swelling; it can also cause shoulder pain or a lump in the lower biceps.
Performing weight training exercises for the biceps -- such as bicep curls -- can make the veins in your arms protrude from the skin's surface, creating bumps. Building muscle and following weight loss strategies reduces your body fat; this allows for muscle definition and the veins in your arms to become more visible.