If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.
Normal body temperature ranges from 97–99°F and is normally considered to be 98.6°F
Body temperature is tightly controlled in warm-blooded animals. Body heat is generated by the chemical reactions inside of cells, and the body is kept at a temperature that is optimal for all of the reactions that need to occur. Having a body temperature that is too low (hypothermia) and a body temperature that is too high (hyperthermia) can both be dangerous.
Hypothermia is usually caused by exposure to cold temperatures. However, hypothermia can also be used in a medical setting to prevent brain damage in certain patients (such as patients that have recently suffered cardiac arrest).
Hyperthermia can be caused by exposure to warm temperatures (such as heat stroke). However, in most cases, body temperature goes up in the setting of an infection. This is called a fever, which is a temperature at or above 100.4°F. Fever can be treated with antipyretic medications, such as acetaminophen (brand name Tylenol), and by treating the underlying cause.
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What we mean by normal
In medicine, using the term “normal” can sometimes be off-putting. Saying something is “normal” implies that everything else is “abnormal.” Additionally, saying something is “normal” may not be accurate, since something that is “normal” for you may not be “normal” for somebody else. Therefore, instead of saying certain values are “normal,” alternative terminology may be to say that these values are “healthy” or “within the reference range.”
Additionally, some values have well-defined cutoffs, while others do not. For example, when looking at hemoglobin A1c levels, a value of 6.5 or greater is always diagnostic of diabetes. On the other hand, when looking at testosterone levels, some use cutoffs of 270–1,070 ng/dL while others use cutoffs of 300–1,000 ng/dL.
The information below represents values that are commonly used as cutoffs. However, depending on the specific source you’re looking at or the laboratory you go to, their values may be a little different.