context: Your body's like a little furnace. It puts out heat all the time. It comes from your body doing the work that keeps you alive. When it puts out a lot more or a lot less heat than usual, it's trying to tell you there's a problem. Not everyone's ânormalâ body temperature is the same. Yours could be a whole degree different than someone else's. A German doctor in the 19th century set the standard at 98.6 F, but more recent studies say the baseline for most people is closer to 98.2 F. For a typical adult, body temperature can be anywhere from 97 F to 99 F. Babies and children have a little higher range: 97.9 F to 100.4 F. Your temperature doesn't stay same all day, and it will vary throughout your lifetime, too. Some things that cause your temperature to move around during the day include: How active you are What time of day it is Your age Your sex What you've eaten or had to drink ( If you're a woman) where you are in your menstrual cycle Your temperature reading changes based on where on your body you measure it. Underarm readings can be a degree lower than what you'd find from your mouth. Rectal temperatures usually are up to a degree higher than mouth readings. A body temperature higher than your normal range is a fever. It's hypothermia when the body temperature dips too low. Both need to be watched. How high is too high when it comes to your temperature? Anything above 100.4 F is considered a fever. You may feel terrible, but on the whole, a fever isn't bad for you. It's a sign your body is doing what it should when germs invade. It's fighting them off. However, if your temperature is 103 F or higher or if you've had a fever for more than 3 days, call your doctor. Also call if you have a fever with symptoms like severe throat swelling, vomiting, headache, chest pain, stiff neck or rash. For children, fevers are a bit more complicated. Call your pediatrician if your child is: Under 3 months and has a rectal temperatures of 100.4 F or higher Between 3 months and 3 years and has a rectal temperature over 102 F Older than 3 years and has an oral temperatures above 103 F Between 3 and 6 months and -- along with a fever -- is fussier or more uncomfortable than usual, or doesn't seem alert Sick enough for you to be concerned, regardless of what the thermometer says If your body loses too much heat, it can be very serious, even fatal. Hypothermia is when your body temperature goes below 95 F. You might think of hypothermia as something that only happens when you're exposed to extremely cold weather for a long time. But it happens indoors, too. Hypothermia is a special concern for newborns and the elderly. Babies may not be good at regulating their temperature. They can lose heat quickly. It's important to keep them warm. A temperature below 97 F is considered too low for babies. Older adults can also struggle to keep their body temperature in a normal range if they're somewhere with intense air conditioning or there's not enough heat. For both the elderly and young children, a below-normal body temperature can be a sign they're sick. Other things can also make you more likely to get hypothermia. They include: Alcohol or drug use Hypothyroidism (an underactive thyroid) Anorexia Stroke Sepsis (overwhelming infection) Parkinson's disease Nerve damage Malnutrition Medicines such as antidepressants, antipsychotics, or sedatives Anesthesia