BBT Charting: No Mid-Cycle Temperature Spike

I get my period every 28 days, but my first three months of charting shows no spike mid-cycle. What can this mean?


Toni Weschler, MS

Toni Weschler is the author of the popular book Taking Charge of Your Fertility. By offering a simple and effective means of identifying... Read more

An absence of a mid-cycle temperature spike can mean one of several things:

  • Your temperatures may not reflect the heat-inducing progesterone produced following ovulation. This is rare, but does happen in some women who are indeed ovulating.
  • You could be having a thermal shift, but you may not have drawn a coverline appropriately in order to accurately interpret your charts. To draw the coverline correctly, identify the first time your temperature rises at least two-tenths higher than the highest of the last six days. Then draw the coverline a tenth of a degree above the highest. In a typical cycle, your temps will remain above the coverline for about 12 to 16 days before you get your period.
  • You may be having a delayed ovulation, with a thermal shift late in your cycle, followed by a short luteal phase of less than ten days.
  • Finally, you may not be ovulating, altogether, although this is not that likely, since women with extremely regular cycles usually do ovulate.
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