What is a triphasic chart? The third temperature rise explained
Updated July 2, 2026
A triphasic chart is a basal body temperature pattern with three levels: a low follicular phase, a post-ovulation rise, and a third rise 8 to 9 days after ovulation. In a published analysis by charting site Fertility Friend, about 12% of pregnancy charts were triphasic, but the pattern also appears in non-pregnancy cycles. Only a pregnancy test can confirm pregnancy.
Key takeaways
- A triphasic chart has three temperature levels: follicular, a post-ovulation rise, and a third rise about 8 to 9 days past ovulation.
- The second rise is driven by progesterone, possibly nudged higher by early pregnancy hormones. It is a clue, not a diagnosis.
- About 12% of pregnancy charts are triphasic in Fertility Friend's published analysis, and many non-pregnancy charts are triphasic too.
- Plenty of pregnancy charts never go triphasic, so not seeing the pattern rules nothing out.
- Only a pregnancy test taken around your missed period, or a clinician, can confirm pregnancy.
What does a triphasic chart look like?
The clearest way to understand a triphasic chart is to compare it with an ordinary two-level (biphasic) chart. Use the toggle below to switch between an illustrative triphasic pattern and a classic non-pregnancy cycle. Tap or hover any dot to read that day. These are example charts for learning, not real user data.
On the triphasic example, temperatures sit low through the follicular phase, step up after ovulation, and then step up a second time about 8 to 9 days later, settling at a third, higher level. On the biphasic example there are only two levels: the temperature rises after ovulation, holds through the luteal phase, then drops back down as the period begins. The third step is the whole story of the word "triphasic": three phases instead of two.
What causes the third temperature rise?
Basal body temperature tracks your hormones. After ovulation, the empty follicle becomes the corpus luteum and releases progesterone, which is thermogenic: it raises your resting temperature by roughly 0.4 to 1.0 F and holds it there for the luteal phase. That is the first rise, the one that confirms ovulation has happened on most charts.
The second, later rise on a triphasic chart is thought to reflect a further shift in the hormonal picture, often a second surge of progesterone in the mid-luteal phase. If an embryo has implanted, the developing pregnancy begins producing hCG, which can support the corpus luteum and may add a small thermogenic push. The honest summary is qualitative: the third rise is a downstream effect of progesterone and possibly early pregnancy hormones, but temperature alone cannot tell you which hormone caused it on any given chart.
When does the third rise appear on a triphasic chart?
The third level usually begins in the mid-luteal phase, most often around 7 to 10 days past ovulation, with 8 to 9 days being the sweet spot people describe. That window overlaps with implantation, which research places at 6 to 12 days after ovulation and most commonly 8 to 10 days (Wilcox, New England Journal of Medicine, 1999). In the example chart above, ovulation is on cycle day 14 and the third rise starts on day 23, which is 9 days past ovulation.
Because the luteal phase is only about 14 days long, a genuine third rise does not leave much runway. If a higher level shows up only in the last day or two before your expected period, it is hard to tell a real third phase from normal day-to-day noise. If you want the earliest reliable test date for your own cycle, the pregnancy test calculator does that math for you.
Does a triphasic chart mean I am pregnant?
Not by itself. A triphasic pattern is more common on pregnancy charts than on non-pregnancy charts, which is why it gets so much attention in trying-to-conceive communities. But "more common" is not the same as "proof". Two things are true at once, and both matter:
First, many people who are pregnant never show a triphasic chart, so a two-level chart does not mean the cycle failed. Second, plenty of people who are not pregnant do show three levels, because progesterone can rise a second time in an ordinary luteal phase. A triphasic chart nudges the odds; it does not settle them. Only a pregnancy test, which detects hCG, or a clinician can confirm pregnancy. For the full side-by-side, see our guide on BBT charts pregnant vs not pregnant.
Watch your own pattern take shape
Safr charts your basal body temperature and your cycle in one place, so a second rise or a drop is easy to spot instead of buried in a spreadsheet.
Triphasic pattern vs a slow rise: what is the difference?
These two get mixed up constantly, but they describe different parts of the cycle. A triphasic pattern is about a second, later step up in the mid-luteal phase, on top of an ovulation rise that already happened. A slow rise is about the very first shift: instead of jumping up in a day, the post-ovulation temperature climbs gradually over three to five days. A slow rise happens right after ovulation; a triphasic third rise happens more than a week later.
| Feature | Triphasic pattern | Slow rise |
|---|---|---|
| Number of levels | Three: follicular, luteal rise, and a higher third level | Two, but the first shift is gradual rather than sharp |
| When it happens | The third level begins about 8 to 9 days past ovulation | During the initial rise, in the first few days after ovulation |
| What it can affect | Sometimes linked to early pregnancy, but not proof of it | Can make the exact ovulation day harder to pin down |
| Common confusion | Late-cycle noise can look like a real third step | A drawn-out rise can be mistaken for a whole extra phase |
The practical trap is reading a slow rise as if it were triphasic and getting hopeful about pregnancy from what is really just a gentle ovulation shift. If your first post-ovulation climb takes several days, that is a slow rise, not a third phase. Our explainer on the slow rise BBT pattern covers what it means for pinpointing ovulation.
How reliable is a triphasic chart as a pregnancy sign?
Treat it as a soft signal, not a verdict. In Fertility Friend's published analysis, about 12% of pregnancy charts were triphasic. That leaves the large majority of pregnancy charts without the pattern, and it says nothing about the non-pregnancy charts that also show three levels. The same analysis found a one-day temperature dip on about 23% of pregnancy charts and 11% of non-pregnancy charts, which is a useful reminder of how much these patterns overlap between pregnant and not-pregnant cycles.
So a triphasic chart is a nice thing to notice, and it is genuinely a bit more common when a pregnancy is developing. It is not a reason to feel certain either way, and it is not a reason to test early. hCG typically becomes reliably detectable around the time of your missed period, so testing from the first day your period is late gives the most trustworthy answer.
Common questions
What DPO does a triphasic chart show?
The third rise most often appears around 7 to 10 days past ovulation, with 8 to 9 DPO described most frequently. That overlaps with the implantation window, which research places at 6 to 12 days after ovulation, most commonly 8 to 10 days. Timing varies from cycle to cycle, so there is no single "correct" DPO.
Can you be pregnant without a triphasic chart?
Yes, easily. Most pregnancy charts are not triphasic at all. The pattern is a bonus clue when it shows up, but its absence tells you nothing. A steady two-level chart with sustained high temperatures through the luteal phase is completely compatible with pregnancy. Only a pregnancy test can confirm it.
Can you have a triphasic chart and not be pregnant?
Yes. Progesterone can rise a second time during an ordinary luteal phase, producing three temperature levels in a cycle that is not pregnant. This is why a triphasic pattern only shifts the odds slightly rather than confirming anything. If your period is late, take a test rather than reading the chart.
Is a triphasic chart the same as an implantation dip?
No. An implantation dip is a single low day, often around 7 to 10 DPO, before temperatures recover. A triphasic pattern is a sustained third rise to a new, higher level. Some charts show both, one, or neither. Neither pattern confirms pregnancy on its own.
When should I take a pregnancy test if my chart looks triphasic?
Wait until you can test reliably, which is generally around the day of your missed period. hCG usually is not detectable much earlier, so a test taken at 9 DPO because the chart looks promising can easily be a false negative. Testing from the first day your period is late gives the most trustworthy result.
Does a triphasic chart always turn into a positive test?
No. Because triphasic patterns occur in non-pregnancy cycles too, a three-level chart is not a promise. Read it as an interesting observation, then let a pregnancy test give the real answer once you are at or past your missed period.
Keep reading
BBT charts pregnant vs not pregnant · What a slow rise BBT pattern means · Pregnancy test calculator: your earliest reliable date
Sources
- Wilcox AJ, Baird DD, Weinberg CR. Time of implantation of the conceptus and loss of pregnancy. N Engl J Med. 1999;340(23):1796-1799.
- Wilcox AJ, Weinberg CR, Baird DD. Timing of sexual intercourse in relation to ovulation. N Engl J Med. 1995;333(23):1517-1521.
- Steward K, Raja A. Physiology, ovulation and basal body temperature. StatPearls. NCBI Bookshelf. 2023.
- Su HW, Yi YC, Wei TY, Chang TC, Cheng CM. Detection of ovulation, a review of currently available methods. Bioeng Transl Med. 2017;2(3):238-246.
- American College of Obstetricians and Gynecologists. Menstruation in girls and adolescents: using the menstrual cycle as a vital sign. Committee Opinion No. 651. 2015.
- NHS. Trying to get pregnant: basal body temperature and your fertile window. nhs.uk. Accessed July 2026.
Chart-pattern frequencies (about 12% of pregnancy charts triphasic; one-day dip on about 23% of pregnancy charts and 11% of non-pregnancy charts) are from a published analysis by charting site Fertility Friend of member charts.