Any of the following 9 factors can alter your basal body temperature, giving you a higher or lower reading than you would get otherwise. So if any of these factors applies to you, pay close attention to your temperatures and make sure to mark them as ‘questionable’ in the Kindara app if they seem incorrect.
1. Restless sleep
You need at least 3 consecutive hours of uninterrupted sleep before waking up to get an accurate BBT (1). If you’re tossing and turning all night, or if you get up to go to the bathroom an hour before you actually wake up, your temperature will likely be affected. Mark it as questionable if this is the case.
2. Moving around before taking your temperature
Remember that you need to take your temperature as soon as you wake up, BEFORE getting out of bed or doing anything. ANYTHING (2). Even snuggling with your partner or just lying in bed awake for a few minutes. Again, if you don’t take your temperature right away, remember to mark it as questionable in the app.
3. Taking your temperature at a different time than usual
If you take your temperature much earlier than you normally do, your temperature may be lower than usual, and if you take it later, it may be higher (4).
If you work night shifts, all of the same rules for getting an accurate BBT still apply. Just try to be as consistent as possible with the time you’re taking your temp. If you work night shifts some days and day shifts on others, take your temperature first thing upon awakening from your longest period of sleep. Track your temperatures along with your cervical mucus and cervical position over the course of a few cycles, and see if you can notice a clear temperature shift. If so, you can continue to track your signs as normal, without having to worry about the varying wake-up times. If not, you’ll need to rely on cervical fluid and cervical position to learn when you’re fertile. Check out this blog for more about how sleep problems and shift work may affect your BBT.
4. Drinking alcohol the night before
Drinking alcohol can raise your temperature the morning after (1). If you have several drinks, you’ll probably need to mark your temperature as questionable the next day. If you like to have, say, a glass of wine or two with dinner several evenings a week, keep track of your temperatures over the course of a few weeks, and on mornings after you’ve had a drink, make a note of it in the app. See if your temperatures appear consistent across your cycle. If so, it may not be necessary to mark your temperature as questionable every time you have a drink.
Stress can affect the body in lots of ways, and your basal body temperature is one of them (2). If you’re particularly stressed, you may notice a change in your temperatures. Mark them as questionable if they seem off.
Travel can be stressful, and especially if you travel to a different time zone, your temperatures may be affected (3). When traveling, wake up at the same time as you normally do (local time) and see if your temperatures appear consistent with the rest of your cycle. If so, you can continue to chart as normal. If not, mark them as questionable until your body adjusts.
Okay, this may be stating the obvious, but it goes without saying that being sick can throw off your temps (1). If sick, mark your temps as questionable or just wait until you’re better to take your basal temperatures.
8. Environmental factors
Using an electric blanket or heating pad that you don’t normally use or sleeping in a much warmer or colder room than normal may affect your BBT. Some people’s bodies are affected by the slightest change in room temperature, whereas others won’t be affected at all by changes. Again, pay close attention to your temperature after nights that you sleep in a warmer or colder room than normal, or nights when you use an electric blanket or heading pad. See if the temperatures after those nights appear higher or lower than normal. If so, you’ll need to mark those temperatures as questionable.
9. Broken thermometer
Finally, if your temperatures WERE consistent but all of the sudden they seem off, you may want to consider purchasing a new battery or another thermometer. Keep in mind that basal thermometers are generally more accurate than regular ones for the purpose of fertility tracking.
If you’re avoiding pregnancy and you need to mark one or several temps as questionable before you’ve confirmed ovulation with a sustained temperature shift, do not assume you’ve entered the infertile phase until you can see a clear pattern of post-ovulatory high temperatures above the coverline. If in doubt, abstain or use protection until your next cycle. If you need to mark a temperature as questionable while in your post-ovulatory phase (learn more about the Phases of the Menstrual Cycle), you don’t need to do anything differently, since you’ve already confirmed that you’ve ovulated and are in your infertile phase.
If you’re trying to conceive and you need to mark one or several temperatures as questionable during your fertile window, make sure to pay especially close attention to your cervical mucus and cervical position during that time.
- Weschler, Toni. (2015). Taking Charge of Your Fertility: The definitive Guide to Natural Birth Control, Pregnancy Achievement, and Reproductive Health.