My Mother Was Diagnosed Last Weekend With A Blood Clot

My mother was diagnosed last weekend with a blood clot in her leg. She is on a blood thinner and pain meds. Today she is throwing up. We are assuming maybe the pain meds are upsetting her stomach, but is this also a sign that maybe the clot broke up and moved to another location? Is this something to be concerned about enough to take to ER or just keep an eye on her in case its the flu or upset stomach from meds?