Traveling across time zones can throw your hormones — and your menstrual cycle — out-of-whack. The further you go, the more likely you are to be affected. This might not matter much if you’re visiting Grandma in Norway. But if you’re beach-bound to meet your new lover, cycle unpredictability may be more annoying. Learning how travel can affect your cycle will help you understand what’s happening in your body, and help you to prepare for any uncertainty.
How does travel affect your hormones?
The menstrual cycle is influenced by travel because of its hormonal relationship to your circadian rhythms. Circadian rhythms are your body’s daily cycles. The word circadian comes from the Latin words circa and dias, meaning around and day. While your menstrual cycle works on a longer timescale, closer to a month, many other functions in the body are happening in cycles of about 24 hours. Changes in appetite, sleep, immunity, healing, body temperature and heart rate are triggered by hormones that fluctuate up at down at certain times of the day and night (1, 2). Circadian rhythms tell these processes when to slow down, speed up or take a break.
The circadian rhythm and menstrual cycles are influencing each other all the time. If you picture a spinning top moving in a big circle, each little spin of the top is the circadian rhythm, and each big circle is the menstrual cycle. If the spinning top gets out of balance, the size and shape of the big circle may change. The top also spins a little bit differently depending on where in the big circle it is at any given time.
When you travel across time zones, we suddenly become exposed to light at different times of the day. This above all throws off your circadian rhythms (3, 4). Research has shown that even a small amount of dim, artificial light triggers hormonal changes in the body (3).
Beyond menstrual changes, travel causes a set of symptoms called jet lag, which include trouble falling and staying asleep, daytime sleepiness, loss of concentration, fatigue, disorientation, decreased alertness and digestive issues. Symptoms are usually stronger when traveling west to east, and can last over twice as long (5). This is because it’s harder for your body to adjust to a shorter day, when you lose time going east (6).
Cycle-related symptoms of jet lag might include (7):
A cycle that is longer than usual (when your period comes late)
A cycle that is shorter than usual (when your period comes early)
A skipped period
Periods that are longer or shorter
Periods that are heavier or lighter
What you can do.
Expect changes: Avoid panicking about pregnancy, or thinking you’ve come down with a mysterious illness. Menstrual changes, within reason, are normal for a cycle or two. Unless your symptoms are severe or persistent, you are probably just fine.
Reconsider your fertile window: Be aware that your ovulation is likely to be off. If you are using a fertility awareness method (tracking basal temperature, cervical fluid, cervical position) to become or avoid becoming pregnant, expect your fertile days to be different from your Clue average.
Prepare: Carry menstrual products even if you might not expect a period. Keep in mind that some countries might not have your products of choice (diaper, anyone?). Also, tampons with applicators are not available in many places, so bring some along if you prefer them. Don’t forget any usual pain medications or other personal remedies.
Track it and carry on: Tracking can be a great way to keep a record of your jet lag symptoms. But if a cycle (or two) is affected, be sure to exclude it from your Clue averages. That way it won’t affect your regular predictions.
It takes time for your hormones to get back into balance when jumping time zones. But if you stay put, you’ll probably be back to normal within a cycle or two. Longer-term changes can happen due to things like constant travel, sleep problems, working a job with night shifts (8) or living in a dark cave with only an iPhone. These can cause consistently irregular cycles that have an impact on bone density, heart health and risk of certain diseases. Any cycle that is consistently irregular should be addressed with a healthcare professional.