The reason the pencil test is so important is because of the effect diabetes has on your body. In addition to causing your blood sugar levels to rise, diabetes can damage your nerves, blood vessels, heart, kidneys, eyes, gums, and feet, especially when left untreated. You can easily become injured while walking around barefoot and have a cut or sore go untreated and become infected when you don’t have sensation in your extremities. On top of not knowing when a wound might require care, losing sensation in your feet can also affect your sense of balance.
In the case of spine issues, a herniated disk, or sciatica, nerve damage that reaches your feet can alert your healthcare provider of the extent of the damage. With multiple sclerosis, numb face, body, hands, and feet are common and preliminary symptoms (via National Multiple Sclerosis Society). At the end of the day, whatever the underlying condition, a pencil test can alert you of it and help you get the treatment that you need.