Time Zones and Insulin

Travelling east-west or west-east across time zones makes eating and injecting insulin at the right time a more complicated business. Do you go by the time in your place of departure or your place of arrival when deciding when to inject? What is the best way of changing over from one to the other?

When there is a time difference between your departure point and your destination, if you use local time to decide when meals and injections are due this will make the time between some of your injections much greater or much less than usual. This can cause you to have too little or too much insulin on board, so there is a risk of your blood glucose level rising or falling dramatically.

There are several ways around this, and the method given below is only one possibility. You should discuss it in detail with your diabetes care team who will help you put together a tailored plan before you travel.

The following method assumes you eat three meals each day.

If you inject quick-acting insulin at each meal

e.g. Novorapid, Humalog, Actrapid, Humulin S, FiAsp, Lyumjev

If you are flying east to west, e.g. from London to Mexico City, the time difference of six hours will make the day six hours longer. Because of this you will need to take an extra dose of quick-acting insulin four to six hours after your third meal of the day. You should eat after this injection. Treat it like an extra medium-sized meal.

If you are flying west to east, e.g. Mexico City to London, the time difference of six hours will make the day six hours shorter. Because of this you will probably be having one less meal on your day of travel so you will need one less injection of quick-acting insulin. You should continue to take your long-acting insulin at the usual times (measured according to local time).

If you take mixed insulin twice a day

 e.g. Humulin M3, Mixtard 30/70, NovoMix30

If you take mixed insulin twice a day and are flying east to west, on the London to Mexico City flight, you could take your usual two injections per day plus an extra injection of quick-acting insulin (supplied by your clinic) eight to ten hours after your first injection of the day. This would be just before the time of your usual third meal. Take your next dose of mixed insulin with your fourth meal. This way you will be taking four meals plus snacks on that day, but the time difference will lengthen the day by six hours.

If you are going on the same west-to-east Mexico City to London flight as above, you could miss your second injection of mixed insulin and instead take an injection of quick-acting insulin (supplied by your clinic). The dose will be about the same as the quick-acting component of your usual mixture. You would then only be having two meals plus snacks on that day, but the day would be six hours shorter because of the time difference.

If you have an insulin pump

If you have an insulin pump, you may need to change your basal rate for the duration of the flight. If you have a hybrid closed loop system, then the pump should do the work for you but if you have a separate glucose sensor, it may be worthwhile, setting your Low alarm to around 5-6mmol/l so that you have lots of time to act if your blood sugar starts heading downwards.

General points

• Remember to eat soon after taking quick-acting insulin (or mixtures containing quick-acting insulin) even if that means eating an extra meal one day.
• Check your blood glucose levels frequently when you are changing time zones.
• Consider setting the Low alarm on your glucose sensor higher than normal, eg. 5-6mmol/l so that you have lots of time to act on any falling sugar levels.
• Discuss the details of how you will take your insulin with your diabetes care team before you go.
• If the time difference between your departure point and your destination is less than three hours you should be able to stick to your usual insulin regimen.
• Make sure your meals are eaten four to six hours apart.
• Ask the airline when the in-flight meals will be served and use them as between-meal snacks or as proper meals, whichever fits your schedule better. You can use your own food to add to what is served or ask for a few extra bread rolls – there are usually some to spare. It is often better to take some of your own food to eat on the plane so you can judge your insulin requirements better.
• Remember that drinking alcohol before or during a flight will affect your blood glucose.
• If flying makes you feel stressed, this will affect your blood glucose too.
• If you are usually quite active, there is a limit to how much energy you can burn up in an airline seat, so doing nothing may give you a higher blood glucose level if everything else remains the same.
• Take some extra food in your hand luggage in case of unexpected delays.

See also Food and Travel, Travel Plans.