A vein that has a tender bump is most likely a “superficial thrombophlebitis”, which in English means a blood clot and inflammation in a vein under the skin. This is usually a harmless condition, but the pain can be quite intense for a few weeks. In addition to pain, tenderness, swelling, and a firm lump or cord, the skin can be red. The limb can hurt when it is extended or moved. Treatment consists of a heating pad or warm compress for 15 minutes three times a day, as well as an anti-inflammatory medication such as ibuprofen, naproxen, aspirin, or acetaminophen. A blood clot such as this can develop in a varicose vein, but a superficial vein blood clot would not cause a varicose vein to develop. Occasionally a superficial blood clot can propagate to larger veins and deeper veins, in which case the condition becomes more severe and needs more aggressive treatment, such as anti-coagulation (see below). A blood clot in deep veins is a much more serious condition, potentially life threatening, and requires physician management. Blood thinning medication (anti-coagulation) may be indicated, as well as other measures, such as compression garments, ambulation, ultrasound examination, and follow up with the treating physician.