Why can't you exercise when there are ketones in your urine?

Its not an: Absolute contraindication to avoid exercise. But in diabetics this suggest that they are at a physiologic point where there insulin needs aren't being met and could evolve into a more concerning, even life-threatening process. Otherwise, without insulin/diabetes issues, ketones in your suggests some element of dehydration or starvation or other acute illness that could be worsened with exercise