Can Phentermine Cause Tingly, Dizzy Body With Racing Heart?

Hello. Three days ago I was prescribed phentermine for weight loss. However, just a moment ago I was sitting down and suddenly my whole body tingled, i felt dizzy, and my heart began to race. What do you suggest I do? Should I only take half a pill a day and continue with the phentermine, or should I stop taking it? Is this normal and how often is it going to happen?