If you have a long-haul trip on the horizon that involves changing time zones, you’re likely making some kind of preparation for that trip. Maybe you’re stocking up on compression socks for the extra-long flight. If you’re a particularly Type A Virgo, you might also plan on adjusting your sleep schedule in advance to stave off jet lag. But if you take hormonal birth control, you should add that to your pre-travel planning checklist—not just remembering to bring it, but figuring out how to take it when you’re about to go to a totally different time zone.

No, this isn’t just a hypothetical problem that only the most anxious of us would come up with while getting ready for a trip. Timing is everything with daily contraceptive pills, and the last thing you’d want to deal with on a trip is an off-schedule period or worse, an unexpected and unwanted pregnancy. But with some pre-planning, OB/GYNs say you can figure out how to keep taking your birth control when changing time zones for optimal efficacy.

Why timing is key for birth control pills

There are two main types of hormonal birth control pills, says Mary Rosser, MD, PhD, an OB/GYN and director of integrated women’s health at New York-Presbyterian/Columbia University Irving Medical Center. First, you have combined oral contraceptives (COC), which use a combo of estrogen and progesterone to prevent pregnancy to prevent ovulation and egg fertilization. While perfect use of these pills entails taking them at roughly the same time every day, COCs can be taken at “any time on a given day,” she says, so long as you take it within a 24-hour period of your last dose.

Meanwhile progestin-only pills (POP), also called the Minipill, work by making cervical mucus thicker and the walls of the uterus thinner to prevent a fertilized egg from implanting. These pills only contain progestin (a synthetic version of progesterone), and often at lower doses than what you’ll find in a COC. As such, the hormone stays in your system for only about 24 hours.

Taking your pill at roughly the same time every day ensures that your body is consistently getting the correct amount of hormones to prevent pregnancy. “When the concentration or amount of hormonal birth control in a person’s blood circulation decreases, it loses control over the brain’s communication to the ovaries. This loss of control translates to a loss of contraception,” says Rachel B. Danis, MD, a board-certified OB/GYN and REI at RMA of New York.

The more you shift around the timing of your daily pill, the higher the risk of the medication not working as intended. “The worst-case scenario is decreased efficacy and an unplanned pregnancy, but more commonly it would be having irregular bleeding or spotting,” says Christie Cobb, MD, a gynecologist and sexual medicine specialist.

How strict you have to be with timing depends on the type of pill you take. Dr. Rosser says missing your usual dose time by a couple hours with a COC is generally not a huge problem, so long as you take it as soon as you can. With the Minipill, you must take it within the same three-hour window each day. If you miss that window, you should take it as soon as possible and then use a backup form of birth control like condoms for the next two days.

How to keep taking your birth control pills when changing time zones

Travel can be chaotic already, so remembering to bring your meds—let alone taking them at the right time—can be a challenge when you’re traversing time zones. To keep on track, you need to figure out what your home time is in your new destination, then ensure that you’re taking a pill every 24 hours, regardless of time zone.

Let’s say you’re traveling from New York to San Francisco, shifting back three hours from your normal time. That means if you typically take your pill at 3 p.m. in New York, you’d just take your pill at noon in the Bay, says Dr. Danis. If you’re traveling from New York to London, which is five hours ahead, you would take it at 8 p.m. while you’re in the UK.

One tip Dr. Danis recommends that works in any time zone? Set an alarm on your phone to remind you to take your pills. These alarms should automatically update to the time zone you’re in, so just set it for your usual pill-taking time and your phone will do the rest. (You can label alarms so that you know exactly what it’s for, even if you’re super jet-lagged.)

Where this gets trickier is if you’re making a big time-zone change. Let’s say you’re traveling from New York to Tokyo, which is 13 hours ahead. Sticking to your 3 p.m. schedule would mean taking your pill at 4 a.m. while in Japan. (Not exactly ideal!)

If you’re going somewhere that necessitates crossing the international date line—which either adds or subtracts a calendar date, making things extra confusing—Dr. Cobb advises consulting a time zone conversion app or chart, like this one, to see what time your dosing time correlates to your destination’s time. She also recommends raising any concerns with your doctor or pharmacist about taking your birth control pills when changing time zones before you leave.

If you take a COC, you have more wiggle room to adjust your pill time to something more reasonable and should aim to take a pill every 24 hours, says Dr. Rosser. In the Tokyo example, this could mean taking your dose before bedtime, or first thing in the morning, to avoid having to wake up at 4 a.m.

To keep coverage with a POP, you need to stay close to your normal dose time. If matching up your regular time would mean waking up in the middle of the night, you can shift your doses earlier gradually by two to four hours, Dr. Rosser says.

To do this for the Tokyo example above, Dr. Danis says you could take your pill before bed at 11 p.m. or midnight in Japan, which would mean your dose is about 18 hours apart instead of 24 hours apart so you’d still be covered. You would then stick with this adjusted time on your trip, and then readjust when you land back on the East Coast.

If you’re determined to keep the afternoon timing of your pill, you could double up the dose. “I would say take two tablets all at once on the day you land in Tokyo, but also use a condom for the first seven days or abstain in case there is a break in hormones,” says Dr. Danis.

In general, all the doctors recommend erring on the side of caution and taking your pill sooner rather than later. If you miss your pills entirely or misalign the timing, there’s a higher chance sex can result in an unwanted pregnancy. To stay covered, use a backup contraception method if you’re sexually active on the trip, says Dr. Cobb. “For the remainder of that cycle, you want to use a barrier method, like male or female condoms to decrease the risk of pregnancy,” she says. It’s not a bad idea to pack your own condoms so you’re not frantically searching in the moment or relying on someone else to have them.

5 other tips to keep up with your birth control while you’re traveling

1. Discuss your travel plans with your doctor beforehand

Before you head out on your adventure, Dr. Cobb advises chatting with your doctor and making a plan for how to handle the time zone change. Ask questions, and tell them how many hours ahead you’ll be so they can help you pinpoint the exact right time to take your pills—or an ideal strategy for adjusting your dose to the new time zone. You can also consult your pharmacist, who is equally qualified to answer questions about medication dosage and timing.

2. Take a picture of the pill’s instructions

Take a picture of your pill’s instructions so you know exactly what to do if you miss a dose. “Before you go on the trip, look at the package insert of your birth control, which is the folded up piece of paper it comes with,” says Dr. Cobb. “Every birth control pill is going to have either a table or paragraph [in that insert] that tells you what to do if you miss a pill.” You can also use these instructions to plan out what time to take your pills. That way if anything happens, you’ll have the relevant information for your specific medication right in your camera roll.

3. Pack enough pills to last the whole trip

It sounds obvious, but double check that you didn’t forget your birth control pills and have enough supply. Don’t rely on finding your pills far from home, because it’s never a guarantee you’ll find your exact medication or have reasonable access to a pharmacy. “You would be amazed by the phone calls I’ve received from all places,” cautions Dr. Cobb. Be sure to fill your prescription well in advance of your trip, too—don’t add a frantic dash to the pharmacy to the pre-trip checklist.

4. Pack your pills in your carry-on bag

It sounds obvious, but be sure to pack your pills in your purse or carry-on, says Dr. Cobb. Never put your medications in a checked bag (and if you have to check a carry on bag at the last minute, remember to pull them out); even the best planning doesn’t matter if your pills are stuck in a lost bag or in the cargo hold of a connecting flight you missed.

5. Consider a different birth control method

Depending on how long you’re gone, it may be worth switching birth control methods entirely if you know it’ll be a challenge to take your birth control pills correctly when changing time zones.

If you’re gone for at least a month, Dr. Cobb advises “seriously considering” switching from pills to a birth control patch or contraceptive ring, both of which require less frequent doses, to minimize errors caused by time zone changes. Long acting reversible contraception methods, like IUDs and implants, mean you don’t have to worry about this at all. “For my patients who are flight attendants or my doctors and nurses that have crazy hours, having that method is a lot more foolproof,” she says.