A collapsed vein is an injury that develops over time from consistently injecting drugs or from intravenous chemotherapy. It is caused by repeated injections to the same area of a vein, using blunt or old syringes, and poor injection technique. Injection of substances that irritate the veins, such as fluids that are hypertonic, vasoactive, irritants, with an extreme pH, or liquid methadone intended for oral use, can also cause permanent vein collapse. Smaller veins may collapse as a consequence of too much suction being used when pulling back against the syringes plunger to check that the needle is in the vein, or removing the needle too quickly after injecting. Veins may become temporarily blocked if the internal lining of the vein swells in response to repeated injury or irritation.

Collapsed veins cause circulation issues in the arms and legs, including itching, tingling, cold feeling, numbness, and discolouration on the skin. If a vein collapses, the body will endeavor to find another vein to use, but collapsed veins may never recover. While collapsed veins are not deadly, they are a sign that it’s time to get help. Circulation issues usually get worse as you age, and you only get one set of veins.

It is important to note that a blown vein is different from a collapsed vein. A blown vein means that the vein has ruptured and is leaking blood, and it happens when a needle goes into the vein and out through the other side. A collapsed vein occurs when the exterior walls of a vein become irritated and swollen, which creates clotting inside the walls of the vein. Over time, the clots harden into scar tissue, and the vein caves inward, restricting blood flow until the vein eventually heals shut.