Short answer: Many people on insulin drive, but low blood sugar can slow thinking and reaction time. Insulin labels name driving as a situation where that matters and ask people with frequent lows or weak warning signs to use caution. In one study, 52% of drivers with type 1 diabetes reported at least one low-related driving mishap in a year. A 2003 survey found drivers with type 2 diabetes, even on insulin, had mishap rates similar to spouses without diabetes.
The Lantus label says low blood sugar can impair concentration and reaction time, which may put the patient and others at risk where those abilities matter, such as driving or operating machinery (section 5.3). It asks prescribers to advise people with frequent lows, or reduced or absent warning signs, to use caution when driving. Section 5.3 of the Humalog label has the same driving wording.
The label says warning signs may be weaker in people with long-standing diabetes, diabetic nerve damage, recurrent lows, or on beta-blockers. See hypoglycemia unawareness.
| Study | Who | Main finding |
|---|---|---|
| Cox 2009, prospective | 452 drivers with type 1 diabetes, 12 months | 52% reported at least one low-related driving mishap; 5% reported six or more |
| Cox 2003, survey | 341 type 1, 332 type 2 and 363 spouses without diabetes, at clinics in 7 US and 4 European cities | Type 1 drivers had more crashes, violations and lows while driving; type 2 drivers were similar to spouses, whether on insulin or pills |
In the 2009 study, "mishaps" included crashes, tickets, losing control, someone else taking over, and moderate or severe lows while driving. They were linked to miles driven, past severe lows and insulin pump use. In the 2003 survey, crashes among type 1 drivers were linked to more lows while driving, checking glucose less often before driving, and using injections rather than a pump, so the two studies point different ways on pumps.
The labels do not give a glucose number to check before driving. The NIDDK lists general steps for anyone at risk of lows: check glucose with a meter or a continuous glucose monitor, which can alarm when glucose drops, keep fast-acting carbohydrate such as glucose tablets within reach, and treat a low with 15 to 20 grams and recheck after 15 minutes.
The NIDDK symptom list includes dizziness, confusion, a fast heartbeat and trouble seeing or speaking clearly, all of which matter behind the wheel. Exercise can lower glucose for up to 24 hours, and alcohol can hide early signs.
In the 2003 survey, half of type 1 drivers and three-quarters of type 2 drivers had never discussed lows and driving with their doctor. The prescriber can say what reading to look for before a drive, and whether licensing rules where someone lives ask anything of drivers on insulin.
Dose Track keeps each insulin dose and any low on one timeline, which makes it easier to answer when the last low was and what came before it.
Read more on Dose Track: Hypoglycemia · Lantus side effects · Humalog side effects · Basal insulin