Those who keep track of their basal body temperature every morning may occasionally notice a reading that is higher than usual. An elevated basal body temperature may indicate different things for different people. For example, it could indicate an infection, which is often accompanied by inflammation and a general ill feeling. Hyperthyroidism is another cause of elevated basal body temperature, and patients with this condition often feel fatigued and restless and have trouble concentrating. For women of childbearing age, a higher-than-normal temperature usually indicates pregnancy or ovulation, which is why some women who are trying to achieve or avoid pregnancy keep track of their body temperature.

For many people, a suddenly high temperature means there is an infection. Those who have a cut or incision may notice that it is red, inflamed and painful, in which case it may be easy to see the source of infection. On the other hand, a viral infection may affect certain parts of the body, with some of the most common signs of viral infection being a cold, pink eye or herpes symptoms. If these or other infections are suspected as the result of an elevated basal body temperature and other symptoms, patients are advised to see a doctor.

Another possible cause for an elevated basal body temperature is hyperthyroidism, because the thyroid gland's tendency to release excess hormones results in a higher metabolic rate. Patients afflicted with hyperthyroidism may have difficulty concentrating and also may have trouble sleeping because of restlessness. Increased hunger, excessive sweating and fatigue also are signs of this condition. Patients who notice these symptoms along with a constantly elevated basal body temperature, are encouraged to see a doctor for diagnosis and treatment.

Women in their childbearing years may notice that their temperature is high for about half of their menstrual cycle, because fertility requires a biphasic pattern that results in a mix of high and low temperatures each month. The first two weeks of the cycle are usually marked by a low temperature, because estrogen rules the body during this time. Once ovulation takes place toward the middle of the cycle, progesterone increases, as does the temperature of the body. If pregnancy is achieved, the elevated basal body temperature stays for a few months, because progesterone will steadily rise, while the temperature will decrease once progesterone levels drop and the menstrual period comes. Thus, some women use their body temperature to give them cues about their fertility, because an elevated basal body temperature that is present for at least 18 days often indicates pregnancy.