DIABETES MELLITUS: In the past, people with diabetes have been involved in almost twice as many motor vehicle accidents as the non-diabetic driving population.  Careful evaluation and medical management can increase their safety.  Even people with diabetes whose disease is well controlled with insulin or oral hypoglycemic drugs may occasionally suffer a hypoglycemic episode.  It is important that the health care professional ascertain the cause of these occasional episodes and change management of the patient.  Before deciding the patient's condition is again stable enough for them to drive a motor vehicle, the health care professional should observe the patient under the new program to ensure it is effective.

Disturbances in the function of the endocrine glands cause many symptoms, from generalized asthenia, muscle weakness, and spasm or tetany to sudden episodes of dizziness or unconsciousness.  Individuals so afflicted should not drive a motor vehicle until these symptoms have been controlled by appropriate therapy.

Problems associated with metabolic diseases, such as muscular weakness, muscular pain, visual disturbances, dizziness, intractable headaches, and/or fatigue propensity, should also be shown under other appropriate profile categories.

Since persons with metabolic disorders may be affected in very different ways, the health care professional should counsel with the patient about any special precautions, limitations, or recommendations appropriate to their case.  These should be reported by the health care professional.

Certain insulin-requiring individuals with diabetes are much more likely than average to have altered consciousness from hypoglycemic episodes.  These individuals have "hypoglycemic unawareness," that is, a lack of the adrenergic warning signs of nervousness and sweating, which should alert the person to eat sugar and reverse the insulin reaction.  The best predictor of which diabetic patient is likely to experience severe hypoglycemia is a history of a recent episode of severe hypoglycemia (under any circumstances) since recurrence of hypoglycemia, and, therefore, reduced appreciation of the hypoglycemic condition is much more likely.

A typical assessment of such individuals includes a history of previous episodes of hypoglycemia-induced unconsciousness, long-duration diabetes, and possibly autonomic neuropathy or beta-blocker therapy.  The health care professional should take these factors into account when determining a safety assessment level.  Also, many episodes of altered consciousness (requiring assistance from another person to reverse) are treated outside facilities and may not come to the health care professional's attention.  Inquiry into such events should be made.

It is strongly recommended that health care professionals counsel all insulin or oral antidiabetic medication-requiring individuals to store in their vehicles, at all times, a source of rapidly absorbed carbohydrate.  Further, blood glucose monitoring just prior to driving should be urged for any diabetic driver with a history of limited awareness of hypoglycemia.

Visual acuity changes, with marked fluctuation in blood glucose concentrations, may affect driving safety.  The patient with impaired vision should not drive until the blood glucose level is brought under control.  Diabetic retinopathy may affect visual acuity and should be checked by a primary health care professional, ophthalmologist, or optometrist, and reported under appropriate assessment categories.

Oral antidiabetic medications, which are highly unlikely to lead to hypoglycemia (unless used in combination with insulin or sulfonylurea), include Metformin, Alpha Glucosidase inhibitors, and insulin sensitizers (thiazolidinediones), GLP-1 agonists, and DPP-4 inhibitors.

PARATHYROID DISORDERS: Hyperparathyroidism with muscular weakness and hypotonia is a contraindication to driving any motor vehicle, unless symptoms are mild or well controlled by therapy.  Individuals suffering from acute hypoparathyroidism with increased neuromuscular excitability, cramps, spasm, and generalized tetany should not drive unless symptoms are mild.

THYROID DISORDERS: Persons with marked hyperthyroidism may experience extreme restlessness, tremor, psychotic disturbance, agitation, insomnia, and, at times, impulsive behavior, which may preclude driving.  Hypothyroidism often leads to somnolence and decreased alertness, which may affect driving safety.

HYPOGLYCEMIA: Individuals suffering from recurring spontaneous attacks of hypoglycemia, causing faintness or unconsciousness, should be carefully evaluated and treated to eliminate such attacks before being allowed to resume driving.

COMMERCIAL INTRASTATE DRIVERS: New applications for K restriction are not accepted.  Insulin-treated Diabetes Mellitus individuals may be qualified for interstate commerce with the Federal MCSA-5870 form.