Accuracy of rectal temps

Would you say rectal temps are more accurate than taking them through the mouth?

Rectal more accurate

You can take a temperature using the mouth (oral), anus (rectal), armpit (axillary), or ear (tympanic). But the temperature readings vary depending on which one you use, and you need an accurate body temperature to determine if a fever is present.

Medical research hasn't determined an exact correlation between oral, rectal, ear, armpit, and forehead temperature measurements. Generally, the correlation of temperature results are as follows:

The average normal oral temperature is 98.6°F (37°C).

A rectal temperature is 0.5°F (0.3°C) to 1°F (0.6°C) higher than an oral temperature.

An ear (tympanic) temperature is 0.5°F (0.3°C) to 1°F (0.6°C) higher than an oral temperature.

An armpit (axillary) temperature is usually 0.5°F (0.3°C) to 1°F (0.6°C) lower than an oral temperature.

A forehead (temporal) scanner is usually 0.5°F (0.3°C) to 1°F (0.6°C) lower than an oral temperature.

In addition 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

What is normal?

Your normal body temperature changes. These changes can be caused by exercise, eating, sleeping and even the time of day - you'll usually find that your temperature is highest in the early evening and lowest in the early hours of the morning.

The average body temperature, taken with a thermometer in the mouth, is 37ºC (98.6ºF), but anywhere between 36.5ºC and 37.2ºC (97.7ºF and 99ºF) can be considered normal. Armpit temperatures are 0.2ºC to 0.3ºC lower than this.

A fever in adults is a temperature of 38ºC (100.4ºF) or above.

What causes fever?

Fever is caused by the release of certain chemicals by the immune system, usually as a result of infection or inflammation. Fever is an important sign that someone is ill and a cause should always be established.

Looking after yourself at home

Not every fever needs medical attention. There are several things you can do to help bring your temperature down and make yourself more comfortable:

Keep the room at a comfortable temperature, but make sure fresh air is circulating

Drink plenty of cold water to prevent dehydration

Get some ice cubes to suck

Take off excessive layers of clothing - small babies or children may be left in a thin vest

Some medicines can help to bring down your temperature. Paracetamol, ibuprofen or aspirin all work in this way. Never give aspirin to children under 16 years of age.

When to contact a doctor

Fever is rarely harmful, but at very high temperatures it can cause problems. A high fever may also be a sign of serious illness. Call your doctor if you're worried, especially if:

You suspect an infection, which might need antibiotic treatment

The fever is higher than 38.5ºC (101.3ºF)

You have a stiff neck, an unusual rash or difficulty breathing

How to check your temperature if you do not have a thermometer

There are some common signs and symptoms when your temperature goes above its normal level. These will vary between individuals and may come and go as long as your temperature is high. If a thermometer is not available, the following signs and symptoms may be a good indication you have a high temperature:

Skin feels hot to touch- Place a hand on your forehead or other part of the body and it will feel noticeably hotter than usual and may be either dry or wet from sweat. NB: do not feel the hands and feet as these can feel cold when the temperature is high.

Flushed skin- When you have a temperature your skin will often become flushed (red). This is particularly noticeable on the face, especially the cheeks. However, it may be more difficult to see on darker skin.

Shivering- As your temperature goes up and down it is common to shiver and feel very cold even when those around you are feeling comfortable.

Feeling hot and cold- Alternating between feeling hot and maybe sweaty, and cold and maybe shivering is an indication that you have a high temperature.

Other signs- Other signs can include feeling tired and weak. Children may show no interest in playing. Loss of appetite is common. However, these symptoms on their own do not necessarily indicate a high temperature.

I did a like on Magpie's post because she taught me some new stuff that I never knew. I know that rectal temperatures are for babies and toddlers. My temperature was taken rectally during my baby and toddler years which was at the end of age 4.

I also agree with RN1993's post too. Your body heat will increase when laying down to go bed. When I was a little one and when my mom sometimes laid in the bed with me, her body heat will increase and make me hot. I am also hot nature.

Back when I was ages 3 or 4, my mom took my temperature rectally on day and the reading was 104 and I had to go to the ER for doctor care. I had a lot of ear infections that caused me to have fever. A mom can recognize her child has fever in the middle of the night by waking her up or moving to the coolest part of the house.

Before taking an oral temperature, it is best to wait at least 20 minutes after drinking or eating something. Back in the summer of 2017, I had a rash on my face from poison ivy and I say around 20 minutes after I had a cookie, I took my oral temperature at the reading was 97.2. Then on the next morning, I woke up with a hot mouth and I took my oral temperature again and the reading 98.4.

Your body temperature can increase after taking a hot bath or being in a steam room. When a mom takes a rectal temperature or her infant or toddler; that is because she has learned that the reading is more accurate.

Absolutely. It' is widely believed throughout the medical community that the rectal temperature is the most accurate.

Absolutely. It' is widely believed throughout the medical community that the rectal temperature is the most accurate.

That is true but for 95% of the patients, the slight differences don't matter.

Furthermore, everyone knows rectal temp is highest followed by oral, the lowest temp is axillary. I have never seen anyone use axillary temp anywhere, let alone in a doctor's office or hospital.

Hospitals use oral, temporal and some use tympanic. I have only seen rectal used in surgery.

A thermometer's accuracy is the same no matter where it is used. The difference is the temperature of the location where it is being used. Precision is not a characteristic of medical practice and therefore it adds little value to the diagnostic process. If the resulting treatment will be different when the temperature reading is a half degree different, then the location being measured would have some importance. ""measure with a micrometer, mark with chalk, cut with an axe"

Rectal is more accurate

By how much though? There can be arguments made that oral is more accurate as well.

Hospitals use oral, temporal and some use tympanic. I have only seen rectal used in surgery.

I recently saw them do a rectal on an adult on an episode of "Untold Stories of the ER". The woman was not "with it" and freaked out when they tried the first time. They had to tie her down. (turns out she had heat stroke)

@Just a guy, the most accurate temperature is core temperature. Core temperature is the temperature of the interior of the body. But this is not practical as it would involve an invasive access, therefore the rectal method is the closest method we have to try and get a core temperature.

In most cases its not critically importance , but there are instances where core temperature or a close approximation of core temperature , like sepsis ( infection), hypothermia ( low temp) , hyperthermia ( high temp ). Here accuracy is very important , that why rectal temperature is chosen .

I worked in ITU ( British equivalent of ICU) and we always used rectal temperature monitoring , but the advent of catheters with a temperature port , we started using theses.

Oral temperatures can fluctuate quite drastically at times, for example after , hot or cold drinks, ambient temperature, people moving the thermometer around in their mouth. So yes it can be accurate , but its affected by actions of the person have the temperature take. With rectal temperatures you have a greater degree of control .

"measure with a micrometer, mark with chalk, cut with an axe"

Those are actually the comedic "rules for precision" which as you noted, is different from accuracy.

Oral temperatures can fluctuate quite drastically at times, for example after , hot or cold drinks, ambient temperature, people moving the thermometer around in their mouth.

Mouth breathing. I know I often have a hard time on the occasions I do take my temperature because I have to focus on keeping my mouth closed. If I'm not careful there is a difference. For the most part I don't worry too much because it really doesn't matter, but still it's there.

Just a little piece of trivia:

Probably the most accurate place to take a person's core temperature is with a thin thermistor probe inserted through the abdomen into the liver. This is as deep or deeper than the rectum for core temperature and is the least affected by anything the patient can do. Patients who are dead usually have their temperatures taken this way. Brain temperatures may also be used.

As Heisenberg said, the more accurately you measure something, the more you will affect what you are measuring.

The health department told me when I came in there sick. Rectal temperature is accurate during a illness or before getting vaccines. No mater what age.

The supposed difference in accuracy probably isn't enough to warrant a rectal temp. in most cases. Oral temps. can be effected by drinking hot or cold beverages, but I'm sure that if you wait a few seconds, it won't make any difference. The fact that modern medicine doesn't rely solely on rectal temps. would support that belief. The majority of American adults(most likely), would not submit to a rectal temp. I can't speak for other countries where this may still be practiced or considered common.

Growing up, my mother used them to age 6, for both reasons of accuracy and safety. If we ran a high fever, she wanted to know how high it really was. Oftentimes, we were congested with the illness and oral readings would not be accurate. She also did not trust us to keep the thermometer under the tongue for the three minutes it took to register. My hospital nurses also did not want to worry about the variables with oral readings and favored rectal readings in our local hospital. Then there was the issue of safety. Mom or my nurses did not want a patient biting down on a thermometer- in those days there were only glass mercury thermometers. I often heard my mother threaten to "use your other end if you don't keep that thermometer under your tongue or bite it"

A rectal temperature taken with a glass rectal thermometer is an exquisite means of capturing a temperature reading. Environmental influences can alter an oral temperature reading such a consuming a hot or cold liquid. However, the most important aspect with regard to taking a rectal temperature with a glass rectal thermometer as opposed to taking an oral temperature with a glass oral thermometer concerns a youngster (or less functional adult) that may be not be capable of keeping a glass oral thermometer intact while placed in the mouth.

I read some things about accuracy. There is a great deal of confusion regarding what constitutes a normal body temperature and what is a fever. “Normal” body temperature is 37 degrees Celsius although this can vary by plus or minus one degree. Body temperature is always higher in the late afternoon and early evening and lower in the early morning. Doctors consider a temperature of 38 degrees or greater to be a fever. The only accurate way to take a temperature is with a thermometer. Digital thermometers are available at any pharmacy and are inexpensive and easy to use. The ways to check the temperature are rectally, under the tongue, under the arm or in the ear. But the temperature readings vary depending on which one you use, and you need an accurate body temperature to determine if a fever is present. Medical research hasn’t determined an exact correlation between oral, rectal, ear, armpit, and forehead temperature measurements. Generally, the correlation of temperature results are: the average normal oral temperature is 37 degrees Celsius, rectal temperature is 0.3°C to 0.6°C higher than an oral temperature, ear (tympanic) temperature is 0.3°C to 0.6°C higher than an oral temperature, armpit (axillary) temperature is usually 0.3°C to 0.6°C lower than an oral temperature. Rectal temperatures are generally thought to be the most accurate way to take your accurate temperature. So if everybody say that the rectal temperature is the most accurate way to take a temperature, I do agree, and I always take my temperature rectally, for pleasure an for the accuracy!

Last post was very descriptive, however they did leave out the vaginal basal thermometer. You do not need this type to normally detect a fever, but it is extremely accurate and is used to forecast ovulation for females.

Last post was very descriptive, however they did leave out the vaginal basal thermometer. You do not need this type to normally detect a fever, but it is extremely accurate and is used to forecast ovulation for females.

A basal thermometer can be used in ANY orifice.

The key is to take the temperature at the same way the exact same time every day before getting out of bed for anything.

I continue to wonder how important it is for an "accurate temperature" when going for a physical exam or doctor visit but it was always necessary and continues to be emphasized. The words, "Accurate Temperature" are now fully associated with my needing to offer a rectal temperature. It's not up for debate, though one could refuse, though what's that about anyway? Considering all that will happen during the exam, the few minutes of lying there with the thermometer nestled between my cheeks is a small price to pay!

Just as an aside, and perhaps some good news on various fronts.

I had a Mom bring her two teen girls, 16 and 13 in today for the first time, both presenting with cold/flu/viral symptoms. I asked Mom if anyone had taken their temps. She said last night her husband did before she got home and it they were 100.8 and 101 respectively and this morning she took them and they were 101.2 and 101.5 respectively. She paused for a second and said, "Oh and those were all rectally". She went onto say that although they use a digital thermometer they find for the entire family that a rectal reading is really the only accurate one and that's that. I noted that I encourage rectal readings to which she nodded in agreement and approval, while the girls just rolled their eyes and blushed, as would be expected.

I have been chatting lately with a few fellow medical professionals on zity and there indeed seems to be a noticeable trend that parents are going back to rectal temps. Much the same as enemas have come back into vogue and the realm of acceptance and common discussion, whether it be for cleansing, prevention, constipation or whatever, they are going mainstream again, as it appears rectal temps are too. The pendulum is obviously swinging.

Julie13 said

I continue to wonder how important it is for an "accurate temperature" when going for a physical exam or doctor visit but it was always necessary and continues to be emphasized.

IT ISN'T

The ballpark is all you need 99% of the time and oral does that just fine. If they just ate or drank something hot or cold, wait ten minutes.

In the late 40’s an 50’s, when my brother, sister, an I, were taken to our pediatrician for our yearly physical. The first thing the nurse had us do, was remove all our clothes. While we were removing our clothes, the nurse always asked mom questions about how we had been health wise the previous year, and if we received an enema the morning of our appointment, as required. When the nurse was through with clothes removal an mom questions, she told us to getup on the exam table and lay on your stomach so I can take your temperature, rectally of course. This was the norm through age 10 or 11. After age 11 the required enema stopped and the rectal temperature changed to oral. I don’t really remember at what age the digital rectal exam started, best I recall it was age 8 or 9, and is still done today at an annual physical. Our grandmother was an RN and for her, the only accurate way to get a body temperature was rectally. When my ex wife started trying to get pregnant with our first child we had to take her temperature three or four times a day rectally and record the date, time, and temperature for her OB/GYN. Therefore, my vote is for rectally being the more accurate method, however, I’m anal erotic, and have been so since before I was 5 years old, so I may be a little bias.

The nurse at health department told me the rectal temperature is good for when you are sick or I'm getting a vaccine. Which is accurate just to make sure that is no fever.

For most purposes, an oral temp is good enough. For cases of hypothermia where you want a core body temp then an RT would be better. My PCP always retakes my blood pressure because the sutomatic cuff the tech uses up front isn’t very accurate. I don’t know that the automatic thermometer is any better but it seems to be about right.

It's easy to look back and say it is not always necessary for a rectal temperature's accuracy. But, in the 60's when I was a child, these thoughts were not really considered. My mother felt that the body's core temperature was what she wanted, that an oral temperature was okay if the rectal was not available. At the pediatrician, it was almost always rectal, as it was my mother's preference for me, and the nurse(s) didn't bat an eye.

Well, this is common knowledge. Rectal temps will always be the most accurate.

Yes! My mother took our temps rectally through high school. When my husband and I decided to start our family, mom gave me her old basal thermometer and taught my husband how to take my chart temp properly. It took almost 3 years, but it worked! i am due this August! mom also gave us one of her rectal fever thermometers and it we used it several times on each other.