Time Zone Crossing
Flying west will lengthen your day, by one hour per time zone crossed, while flying east will shorten it by the same amount.
North or South, obviously, makes no difference.
Lets take an example. Say you leave home on a Friday at 8am and are going on a 14 hour flight. You would expect to arrive at your destination at 10pm that same day.
However you are actually going to fly west and will be crossing 8 time zones. That means that although you still leave at 8am on Friday you will arrive at your destination at 6am on Saturday.
For a normal person crossing a number of time zones may leave you tired and disoriented. This is because your normal biorhythms are affected – basically your body clock tells you it should be one time but your normal senses tell you it is another.
This is what is commonly called ‘jet lag’ and can make one feel disorientated, unable to sleep, totally exhausted, not wanting to eat and suffering from a headache.
For a diabetic there is an added problem – when to take ones meds and how much?
Our schedules are carefully worked out to suit our 24 hour day. But what happens when out day is suddenly lengthened or shortened by a number of hours?
The cardinal rule here is to rest frequently and not to try and achieve the normal tight control. Be happy with adequate control.
It is far better to have slightly elevated Bg’s than to have a hypo in a crowded aeroplane or in a foreign country where few speak you language and so don’t understand what is happening to you. Most of us dislike being considered ‘drunk and disorderly’ by onlookers!
For those of us on oral meds this change in time is not much of a problem. It is simpler to just take our meds at the normal hour, wherever we may be.
If your day is going to be ‘shortened’ by a significant number of hours and you take Metformin or one of the thiazolidinedions or sulfonylureas you can choose to skip a dose and have slight hyperglycaemia for a few hours rather than take two doses too close together and risk the chance of a hypo.
If on carbohydrate absorption inhibitors like acarbose, or a nonsulfonylurea secretgogues like Prandin or Starlix then you should continue to take it as usual before your meals.
For those on insulin therapies however it is, as always, a bit more complicated.
If you fly west and gain hours you may need more insulin and east means losing hours and possible less insulin.
Usually one only has to worry if one is crossing 3 or more time zones. However this is a very individualistic thing and need to be adjusted to suit your own personal situation.
The first, and often simplest, way to go is to speak to your doctor or diabetic advisor a few weeks before leaving, tell them where you are going and the time differences and let them help you calculate your insulin requirements, both for the actual flight itself and then for the period of your stay in your chosen destination.
It may be that they can suggest a change in schedule, say from a twice a day routine to multiple injections for the duration of your holiday, or they may just suggest giving yourself more or less insulin at particular times or a change in the type of insulin you are using.
Humalog (insulin lispro) for example, does not have to be injected the usual 35-40 minutes before a meal but can be given immediately before it. This is a very useful attribute as there is no way you are going to be able to predict when your in-flight meal will arrive. All sorts of things can delay it, from late departures to turbulence.
You also do not know what it will contain. Some ‘diabetic’ meals have arrived containing virtually no carbohydrates at all! That is why it is often better not to ask for a special diabetic meal but just go with the normal one and eat what you can from it.
As I have said, this is a very individualised situation and only you and your diabetic advisors will know what is best for you.
What to do if you do not have, or cannot get to a helpful diabetic advisor.
At one time the general advice given was – increase or decrease your insulin by 2-4% for every time zone crossed. This is a bit hit and miss in my opinion though folk swear it works.
Other advice is as follows:-
If on a multiple injection treatment
Eat every 4-5 hours during the flight (you may well have to take your own food) and, up until your bedtime at your destination, use your short acting insulin to cover the meals. This will mean more insulin when going west and less when going east.
Once your new ‘destination bedtime’ has arrived give yourself your usual bedtime dose of bedtime insulin and from that point onwards you can carry on your regime as normal.
If on a 2 dose treatment
This is by far more complicated. It would be better if you could adjust to a multiple treatment a while before your holiday.
However if you cannot do this then the following may help.
1. If travelling westward take some extra short acting insulin on the plane with you to use before each meal.
Once you have arrived give yourself the usual night time insulin at the new destinations ‘night’.
Now carry on your treatment schedule as normal.
2. If travelling eastward on a night flight then do not take your mixed insulin at dinner before flying.
Take a dose of only short acting insulin before dinner at home, then once on the plane take another dose before the evening meal is served. Usually there will be at least 4-5 hours before your home dinner and the time they serve you a meal on the plane.
If breakfast is served within 5 hours of your last insulin then take your normal dose of short acting insulin plus your intermediate acting insulin, but reduce the latter by 3-5% per hour change undergone (time zone crossed).
If breakfast is more than 5 hours from your last meal you may have to take another small dose of short acting insulin. When breakfast does arrive take your usual short acting insulin but reduce the intermediate insulin by 20-40%.
3. If travelling eastwards on a day flight then take your usual insulin with breakfast.
Before dinner take the usual short acting insulin but reduce the intermediate insulin by 3-5% per hour change (time zone crossed).
Clinical.DiabetesJournals also offers advice on this subject.
How to cope with time zones if you use a pump.
The easiest way to cope is to set a temporary basal rate, this being the lowest basal rate for the amount of time you will be travelling. Then taking a bolus dose at every meal.
On arrival at your destination you need to turn off the temporary basal rate and to change the clock on your pump to the new time.
You will need to keep a close check on your blood sugars during travel and keep checking until they have returned your normal status.
And remember to change your pump clock back to normal time when you get home!