All iLive content is medically reviewed or fact checked to ensure as much factual accuracy as possible.
We have strict sourcing guidelines and only link to reputable media sites, academic research institutions and, whenever possible, medically peer reviewed studies. Note that the numbers in parentheses (, , etc.) are clickable links to these studies.
If you feel that any of our content is inaccurate, out-of-date, or otherwise questionable, please select it and press Ctrl + Enter.
Basal temperature with delayed menstruation
Medical expert of the article
By measuring the basal body temperature, women determine the period of ovulation of their cycle - the time of the most likely fertilization. What is the basal temperature with a delay in menstruation and why?
Basal temperature during early pregnancy and delayed menstruation
Basal body temperature is considered, measured in the oral cavity or rectally in the morning - without getting out of bed, that is, while the body is at rest. Therefore, the basal temperature is not measured during the day and in the evening with a delay in menstruation. Why?
Because a person's body temperature drops at night, and when it is measured immediately after waking up, factors that can somehow affect thermoregulation are excluded, in particular: food intake, physical activity, stress, weather, water procedures and much more.
For information on how to measure basal temperature with a delay in menstruation and how, based on the data obtained, correctly build a graph of basal temperature during pregnancy before a delay in menstruation, read in detail in the publication - What is basal temperature and how to measure it
During the first 14 days, the cycle is regulated by estrogens, and before ovulation - that is, before the egg leaves the mature follicle and enters the fallopian tube (fallopian tube), where it can be fertilized - the basal temperature is usually from +36.1 up to + 36.4 ° С, although these figures have individual options.
An increase in basal temperature by 0.2-0.6 ° is one of the signs of ovulation , during which its indicators can reach + 36.6-37.3 ° C. What is the reason for this? The only reason is an increase in the woman's blood levels of progesterone, a hormone produced by the corpus luteum of the ovaries. It is assumed that the thermogenic effect of progesterone is mediated through the thermoregulatory center of the hypothalamus. 
About a day after ovulation, the progesterone level rises sharply (from 1-1.5 to 3-4 ng / ml) and continues to rise until it reaches a peak (10-20 ng / ml) a week after ovulation - to support the implantation of a fertilized egg into the uterus, and also help maintain pregnancy by preventing menstruation. All the details - Progesterone during pregnancy 
Then there are two options. If the basal temperature does not decrease, this may indicate that the level of progesterone remains high due to the onset of pregnancy. In this case, menstruation does not occur on time (that is, the woman notes a delay in menstruation), and the temperature indicators will remain high throughout the gestation. What should be the basal temperature during early pregnancy? Within + 36.6-37.4 ° С, but again, there may be individual nuances. You can learn about them from the publication - Basal temperature during early pregnancy
It is easy to guess what the basal temperature during pregnancy is before the delay in menstruation. When conception has occurred, then during these two weeks before the missed period of the onset of menstruation, the basal body temperature can fluctuate from the same +36.6 to + 37.4 ° C. Useful information also in the material - All about the first weeks of pregnancy
The second option: if the basal temperature indicators decrease, it means that the level of progesterone decreases, that is, fertilization did not occur, and the endometrium prepared for it collapses, which leads to the onset of menstruation. 
Delayed menstruation at low basal temperature
If a woman's thermometer does not rise above + 36.5 ℃ even during the high temperature phase (when ovulation should occur), this means that the basal body temperature is low.
Of course, a delay in menstruation at a low basal temperature is not excluded. The main reasons for their delay - menstrual irregularities - are general fatigue, lack of sleep, stress, underweight, obesity, excessive exercise, insulin resistance, endocrine problems (with the pancreas or thyroid gland), hormonal contraception, the onset of menopause (which some women may start before age 40-45). 
In addition, one should take into account the likelihood of anovulation - the absence of ovulation, when the egg is not released, and the hormones do not enter the luteal phase. Anovulation is essentially a prolonged follicular phase. And this can be with amenorrhea - the absence of menstrual bleeding, not related to pregnancy and indicating health problems and hormonal imbalance.
High basal temperature in the absence of pregnancy
In many cases, women may complain that the basal temperature is 36.9-37.3, and the pregnancy test is negative.
Firstly, there are many good reasons not to place high hopes on an early pregnancy test, since all existing tests are based on the detection not of progesterone, but of the hCG hormone - human chorionic gonadotropin (synthesized by the chorionic cells of the implanted egg, which is transformed into the embryo). 
Secondly, even when the progesterone level is slightly higher, this does not mean that fertilization has taken place and the woman is pregnant. Sometimes there are several days with higher temperatures due to residual volumes of progesterone from the last cycle, but they will drop again as soon as your period begins. 
A prolonged increase in basal temperature may be associated with:
- with hyperthyroidism, in which there is an increase in the production of thyroid hormones (which increase the rate of cellular metabolism);
- with prolonged excess nutrition;
- with polycystic ovary syndrome (due to the action of vasoactive peptides of endothelial growth factor - VEGF, released from ovarian cyst cells.
- with the presence of malignant neoplasms, the cells of which have a high level of metabolic activity;
- with an iatrogenic complication of ovarian stimulation with hCG analogs during IVF procedures (ovarian hyperstimulation syndrome). 
It must be borne in mind that fluctuations in daily temperature indicators within a few tenths of a degree depend on the phase of the menstrual cycle. So, the temperature during the entire luteal phase of the cycle will be higher than in the follicular phase. When the luteal phase begins with ovulation, the temperature rises and remains high for 12-16 days (one day with a high temperature does not indicate ovulation). When the follicular phase begins with your period, the temperature will drop and stay low.