Why is my left foot swollen, red,warm? it used to happen only in the summer, but now it happens when i sit fot too long. i have hbp but dont take meds

There are two issues: Here. Having high blood pressure and not taking meds is a serious recipe for disaster. I would encourage you to take your meds as prescribed. For your unilateral foot swelling there are many possible causes including venous insufficiency, gout, infection, s/p injury, DVT and feel this should be examined by a medical doctor or podiatrist as well.