basal body temperature charting

Charting Your Basal Body Temperature Information and FAQ

basal body temperature / fertility charting

Basal thermometers can be purchased online here.

This page is a basic guide to charting your basal body temperature. You can use a free online BBT charting service like OvaGraph and buy a BBT thermometer and you will be all set to go. For more details on charting, you should consult one of the many books on this topic. There are some frequently asked questions and answers after the general instructions.

You can also chart your basal temperature online using a free service provided at This offers a number of advantages over traditional "paper" charting, and their proprietary software even helps to identify your ovulation date.

Charting your BBTs is really pretty easy. Basically, what you are doing is taking your temperature first thing each day and plotting the temperature on a chart. What you are looking for is to see a shift of at least .4 degrees Fahrenheit after ovulation making your chart biphasic (showing low temperatures before ovulation in the follicular phase, and higher ones after ovulation in the luteal phase). Be sure to use ovulation tests in conjunction with your basal charting to provide you with an accurate sense of your most fertile time of month.

  1. Take your temperature first thing in the morning before you get out of bed or even speak -- leave your thermometer at your bedside within easy reach so you don't have to move much to get it. If you use a glass thermometer, make sure you shake it down before going to bed.

  2. Try to take the temperature at as close to the same time each day as possible -- set an alarm if you need to. Staying within a half hour either side of your average time is a good idea because your temp can vary with the time (i.e., if you usually take your temperature at 6 a.m., it is OK to take your BBT between 5:30-6:30, but the closer to 6 the better). The normal variation is by up to .2 degrees per hour -- lower if you take your temperature early, higher if you take it late.

  3. It is best to take your BBT after a minimum of 5 hours sleep, and at least 3 in a row is preferable.

  4. You can take your temperature orally, vaginally, or rectally -- just stay with the same method for the entire cycle.

  5. You should try to place the thermometer the same way each day (same location of your mouth, same depth vaginally and rectally).

  6. Plot your temperature on your chart each day, but refrain from reading too much into it until the cycle is done.

  7. Some women, not all, have a temperature drop when they ovulate. If you see this drop, it is a good idea to have sex in case you are ovulating.

  8. What you are looking for is a temperature shift of at least .4 degrees over a 48-hour period to indicate ovulation. This shift should be above the highest temperatures in the previous six days, allowing one temperature to be thrown out as inaccurate (fluke, illness). Perhaps the best way to explain this is to show an example.

    BBT Chart

    In the image above, the seven BBTs before ovulation are 97.2, 97.3, 97.8, 97.4, 97.2, 97.3, 97.0 then it jumps to 97.7 and then 98. Ovulation most likely occurred on the day with the 97.0 and you can comfortably draw a coverline at 97.6. You just ignore the 97.8 on day 10.

  9. After you see a temperature shift for at least three days, or at the end of your cycle, you can draw a coverline between your follicular phase and luteal phase temperatures. With luck, it is easy to see a clear shift and draw your line between the highest follicular phase BBT and the lowest luteal phase BBT as in the sample above. The main reason for drawing this line is just to clearly delineate that your chart is biphasic.

  10. Look at the chart at the end of the month to analyze what happened.

  11. Chart for a few months and look for patterns.

  12. If your temperature stays up for 18 days or more after ovulation, you should test for pregnancy.

One thing to note is that women with ovulatory cycles but with irregular cycle lengths, the greatest variation from cycle to cycle should be in the follicular phase. The luteal phase should be relatively constant (within 1-2 days). So if one has a cycle that ranges from 28-34 days, and a luteal phase of 14 days, ovulation would occur somewhere between days 14-20 -- not the middle of a cycle, not day 14 . . . This is the biggest mistake women with long cycles make when trying to conceive.

Charting Cervical Mucus and Cervical Position

If you want a clearer picture of your cycle, it is best to combine charting your BBT with charting your cervical mucus (CM) and perhaps also charting your cervical position.

There are several ways to chart your mucus, and you have to find the approach that is best for you. You can simply examine your toilet tissue after wiping. You will see more mucus after you have a bowel movement. Another way is to insert two fingers and gently take a little pinch of mucus from the cervix.

The easiest positions for most women would be sitting on the toilet, one foot up on the toilet or bathtub, or squatting. If you have trouble reaching, you can ask your partner to check for you. For most, the best position to do this would be for the woman to get on all fours on the bed, or chest down on a pillow, and let the partner insert fingers from behind. Otherwise your partner will be crawling around on the floor!

Cervical Mucus

Mucus varies from dry, to sticky, to creamy, to egg-white (EW) before ovulation in most women. Note that there is now a product on the market for trying-to-conceive women, FertileCM, that is designed to help encourage the production of abundant "fertile-quality" cervical mucus. Also, BabyDance Fertility Lubricant is now available to ensure sperm-friendly lubrication while trying to conceive.

  • Dry is when there really isn't much mucus to get your fingers on.
  • Sticky is when you get enough mucus for your fingers to feel sticky or tacky.
  • Creamy might be whitish and feels somewhat like lotion when you rub your fingers together. This mucus can be fertile, but isn't always.
  • Egg-white cervical mucus (EWCM) is called that because of its resemblance to raw egg whites. It is either clear or streaked and stretches an inch or more. Sometimes it is watery. FertileCM can help to produce more EWCM.

After ovulation it is normal to have some dry, sticky or creamy mucus, and some women have watery mucus or a little egg-white again right before their menses begins.

Cervical Position

If you are planning to chart cervical position in addition to BBTs and mucus, it makes sense to chart your mucus by feeling your cervix (or having your partner do it).

You cervix has a pattern each month . . . it should start out low, closed and firm. Around ovulation it shifts upward, gets softer and feels more open. The difference is slight -- like the difference between feeling your nose (firm) and feeling your lips (soft). It should only stay high for a day or two around ovulation and you may catch it in transition for a day on either side. The rest of the luteal phase (after ovulation) the cervix should be low. It is often soft right before menses. It tends to shift up if you are pregnant.

One caution is that you shouldn't read too much into cervical position alone since how full your bowels are can make a difference as to how high it feels.


Basal Body Temperature Questions

Q: What will my BBT chart tell me?

A: The goal is to find out if you are ovulating and help you time intercourse. If you see a definite biphasic chart, that's a good sign. You can also tell whether your luteal phase is long enough if your temperatures are up for at least 12 days after ovulation.

Q: How long should my temperature stay up after ovulation?

Ideally, 14 days. Some doctors say anything over 10 days is acceptable, but it really makes sense to test for luteal phase defect if one typically shows 12 days or less of high temperatures. You can test for luteal phase defect with a serum progesterone level and/or an endometrial biopsy. Many doctors will want to see two cycles of low progesterone or out of phase biopsies before making a definite luteal phase defect diagnosis.

Q: My temperature dropped for a day in the luteal phase, does that mean this cycle is a bust?

A: Not unless it stays down. Some people have a short drop that may go well below the coverline that is a secondary estrogen surge (which may be accompanied by mucus).

Q: How long should I chart before seeing a doctor if I suspect infertility?

A: Good question! If your cycles are irregular, you shouldn't waste time on BBTs alone -- see a doctor and find out what may be causing the irregularity. If you do have normal-length cycles and decide to start charting, you only need to wait about 3 months to establish a problem and seek help. For example, if you have a 28-day cycle, but ovulate on day 18, and that happens 2-3 months in a row, you should see your doctor. Otherwise it depends on your age and urgency. It's not a bad idea for everyone to get preconception advice and bloodwork -- test for immunities to rubella, chicken box, fifth disease, also test for anemia and thyroid function at a minimum.

Q: What are average BBTs?

A: The average range of BBTs is between 97.0-97.7 before ovulation and 97.7-99.0 after ovulation. Ideally, a woman's temperature will not bounce around more than .5 degrees in the follicular phase and will stay above the coverline during the luteal phase.

Q: My BBTs are lower/higher than average, what does this mean?

A: Either case warrants checking your thyroid. Low BBTs are often a sign of hypothyroid which can cause some fertility and pregnancy problems. Excessively high temperatures may indicate hyperthyroid.

Q: I did and ovulation predictor kit, how long after the positive should my BBT rise?

A: You should ovulate 12-48 hours after the positive ovulation predictor test, and your BBTs should go up within 48 hours of ovulating. It can take up to 4-5 days to see the rise, but ideally you see it within 3.

Q: My chart looks more like the Rocky Mountains than anything else, what does that mean?

A: Most likely a) you are not taking your BBTs consistently or sleep erratically, b) you are taking your BBTs orally and you sleep with your mouth open, or c) you are not ovulating. If being more consistent, or switching to taking your BBTs vaginally or rectally, doesn't help, you should go to the doctor to have your hormone levels checked out and see what may be causing your anovulation.

Q: How late in a cycle can one ovulate?

A: It is possible to ovulate very late in a cycle -- there is not any day limit -- so a long cycle doesn't mean there is no hope. Long cycles do, however, reduce opportunities to get pregnant and warrant looking into. It is also a good idea to have at least one cycle every 3 months, brought on by medication if needed, so that the uterine lining does not become too thick.

Q: Can I tell I am pregnant from a BBT chart?

A: You are most likely pregnant if your BBTs stay up for 18 or more days after ovulation. It is also common to see a triphasic chart, a second shift sometime during the luteal phase, when pregnancy is achieved.

Q: Do I really need BBT thermometer, or will a fever thermometer do?

A: A BBT thermometer is more reliable and more accurate. In glass thermometers, fever ones are only accurate to .2 degrees Fahrenheit. You really need it to be accurate to .1 degrees. The main plus of the digital BBT over a fever BBT thermometer is speed. The BBT digital is more accurate for some people, and it only takes 30-60 seconds, which can matter if you are waiting to go to the bathroom first thing in the morning. The digital ones are harder to break and remember the temperature for you if you don't want to chart it immediately.

Q: Are my BBTs as accurate if I am taking fertility medications such as Clomid or injectibles?

A: In a word, no . . . but that doesn't mean they don't tell you something. Clomid often causes elevated BBTs around the time of taking the medication, and it appears to be more common to have a triphasic BBT on medications without pregnancy. It is also more common to have a long luteal phase without pregnancy. Other monitoring is more reliable when on medication.

Q: Will taking progesterone raise my BBTs?

A: It may raise your BBTs, but natural progesterone usually only causes a minor elevation (.1 or .2). Progestins like Provera can raise BBTs as well.

Q: My BBTs were up for more than 18 days and I am not pregnant. Why?

A: That's a question for your doctor. If you were on medication for fertility problems, that could cause an extended luteal phase. It is also possible for a corpus luteum cyst to lead to a longer luteal phase. The best thing to do is see your doctor for a blood pregnancy test, exam and ultrasound.

Mucus Questions

Q: How can I tell fertile mucus from semen?

A: Fertile, egg-white mucus should stretch repeatedly in only one of two strands. Semen tends to be a little cloudier, and often stretches in several spiderweb-like strands. You may be able to stretch it a few times, but then it will begin to break.

Q: What is this about taking Robitussin to help with cervical mucus?

A: Plain Robitussin, or any generic with the guaifenesin as the only active ingredient, is an expectorant and helps thin mucus in your body, including cervical mucus. It does not create mucus for you, but can thin out thick mucus (a common side-effect of Clomid). The recommended dose is 2 teaspoons 3 times a day with a full glass of water, but you can take up to the maximum dose on the label. It should be started about 5 days before ovulation and continued through ovulation day. The water is very important since your body needs the fluid to create the mucus, and the guaifenesin can cause constipation. See the Robitussin FAQ.

Q: I've heard I can use raw egg whites if I don't have enough fertile mucus, is this true?

A: It is suggested in the book Taking Charge of Your Fertility by Toni Weschler, but it probably is not a good idea - most eggs in the United States contain salmonella and you risk the possibility of becoming infected. It would be better to use something else as a lubricant. The rest of the book is great, but this is one piece of advice that may be safer to avoid.

Q: What are some sperm-friendly lubricants?

A: Most lubricants will kill off some sperm so it is best to use as little as possible. It is reasonable to use a small amount of over-the-counter brands such as Astroglide, or ask your doctor to order you some FemGlide. Saliva is not a sperm-friendly medium, nor is water. Anything petroleum-based, such as Vaseline, should be avoided.

Related Articles