Update [January 14th, 2015] — We've had a few people report issues with long-term reliability and accuracy of our choice. (About three, which is three people too many.) While we reevaluate and reformat this guide, we would suggest waiting to make a purchase. If you need a good thermometer today, our second option, The Vicks, is a solid choice.
Having a good, trustworthy thermometer makes taking a baby's temperature easier and less traumatic for both baby and parents. If I were buying one thermometer for my baby today, I'd buy the Safety 1st Advanced Solutions High Speed Rectal Thermometer. ($11) Yes, we are indeed recommending a rectal thermometer—more on that in a bit—because it offers accuracy, reliability and speed at a reasonable price.
After 35 hours of researching 30 models of thermometers priced between $4.50 and $95 and testing 13 of those models on a typically squirmy nine-month-old and a compliant four-year-old, as well as to speaking to pediatricians and a physicist from the National Institute of Standards and Technology, the Safety 1st Advanced Solutions High Speed Rectal Thermometer came out on bottom—er, top.
Who Should Buy This?
Expectant parents and parents of babies (especially those younger than three months old, but easily those up to a year old) looking for a reliable means of taking their child's temperature. It's pretty much a guarantee that if you have a baby, that baby is going to run a fever at some point (or you're just going to think your baby is running a fever when in fact everything is fine—because really, parenting = worrying), and you're going to need to know the specifics of your child's temperature.
Mercury vs. Digital Thermometers
Growing up, many of us remember our parents using an old-fashioned mercury thermometer on us. While especially accurate for rectal readings (when kids couldn't run it under hot water or sneak a hot drink before popping a thermometer in their mouth), mercury thermometers came with plenty of downside. Because they were made of glass, they could break fairly easily (especially during the initial shaking down of the mercury prior to temperature taking), potentially exposing family members to the mercury, a potent neurotoxin, inside. They were challenging to read; remember holding them up to the light and searching endlessly for that minute red line?
Additionally, they took a damn long time to get an accurate reading (directions on one lodged in a relative's medicine cabinet required four minutes per reading, which is pretty much an eternity when trying to take a baby's temperature rectally). The toxicity of the mercury and its contribution to environmental pollution outweighed the accuracy of those thermometers, though, and in recent years, federal and state authorities lobbied to make it impossible to purchase medical mercury thermometers. In 2011, the National Institute of Standards and Technology (NIST) closed its calibration service for mercury thermometers, which had ensured the accuracy of mercury thermometers used in chemical, pharmaceutical and petroleum facilities, and the closing of which marked the final phase-out of mercury thermometers Inside Science News Service reported. (Note: if you still have a mercury thermometer in your medicine cabinet, the Environmental Protection Agency offers detailed advice of what to do in case of thermometer breakage to keep yourself and your family safe from exposure.)
Even before mercury thermometers were on their way out, digital thermometers were on their way in. While mercury-based thermometers function by the mercury expanding and contracting according to changes in temperature (and thus moving up or down the tiny glass tube in response to temperature changes), digital thermometers designed for oral, rectal or axillary use are typically thermistor-based. Others like tympanic and temporal artery thermometers use infrared technology. Generally speaking, digital thermometers are faster and easier to read, but they may not seem as reliable as the old mercury thermometers (although the NIST says that digital thermometers are in fact superior overall to mercury-based ones). We read endless complaints about inaccuracy of readings, including some thermometers that may consistently read a few degrees high or low (when someone knows their temperature is normal) and others that offer dramatically different readings in a single setting. It's enough to drive some to return to the simple check with the back of your hand method, but alas, most pediatricians' offices want specific readings (especially for a baby younger than three months) when you're calling to request a sick visit.
Which Style of Thermometer Should I Buy?
If you've ever Googled baby thermometers, searched for them on Amazon, or walked through a big box store's thermometer aisle while registering for baby gear, you already know that there are myriad options. Rectal, axillary (armpit), oral, temporal artery (forehead), tympanic (ear), pacifier, disposable strip, non-contact infrared…the list goes on and on. The good news? We can offer you some guidance. The bad news? You might not like what we found.
Rectal thermometers: Sadly for the squeamish, these remain the gold standard in medicine according to the American Academy of Pediatrics (AAP), the American Academy of Family Physicians (AAFP), and the pediatricians with whom we spoke, including Dr. Jennifer Shu, an Atlanta-based pediatrician, medical editor of healthychildren.org (the official parenting website of the American Academy of Pediatrics), and a co-author of Food Fights and Heading Home with Your Newborn. So why should you stick a thermometer up your baby's bum, despite fearing you'll puncture something? Because rectal temperature is closest to core body temperature, which is the most accurate assessment of whether or not your baby has a fever. Although healthychildren.org states that rectal temperatures can be taken up to age 3, you may well find that your toddler has no interest in allowing you to do so—which is totally fine. Rectal temperature readings are most important for babies younger than three months, for whom a reading of 100.4 or higher is an indication you should take your baby to the pediatrician for further examination. Consumer Reports suggests that for babies younger than three months, "every tenth of a degree counts. The difference between a temperature of 100.3 degrees F and 100.4 degrees F, for example, can determine whether you stay home or take your baby to the emergency room." But really, if your babe is in the 100-range, just call your doc, advises Dr. Shu, and don't sweat the tenths of degrees.
Axillary (armpit) thermometers: Useful as a screening tool at any age (less so for babies younger than three months, for whom a temporal artery thermometer is preferred), but less accurate than other methods—and thus not a diagnostic tool, according to healthychildren.org. Don't rely on axillary readings if you're concerned your child is sick.
Oral thermometers: These are best left to kids ages four or five and up who can be trusted to leave the thermometer in place under their tongue for the duration of the reading.
Temporal artery thermometers: These are gaining big ground these days in the marketplace, and you may encounter them at your pediatrician's office. They read the infrared heat waves released by the temporal artery (located just below the skin, across the forehead). They're currently recommended for use in babies over three months of age (and as a screening tool in babies younger than that), but new research indicates they may be acceptable for use in newborns.
Tympanic thermometers: These read the infrared heat waves released by the eardrum. They're not considered accurate in babies younger than six months because their ear canal is so tiny. Small, curved ear canals and wax build-up can affect readings, as can improper positioning.
We excluded other types of thermometers like pacifier thermometers, wearable thermometers, and forehead strip thermometers from consideration because they are typically less reliable and are not recommended by the medical community.
What Makes A Good Baby Thermometer?
In a word: Accuracy.
Okay, let's make that two words: Accuracy and consistency.
Parents want a thermometer that they can trust the first time and every time they take a reading. Beyond that, good design is key, and for a rectal thermometer, that means a short probe and a design such that it's nearly impossible to over-insert it into the rectum.
Other features in the category which are nice to have but not must-haves: a memory feature, allowing you to keep track of several of the most recent readings to help track if your child's temperature is climbing; a large, backlit display (especially helpful for middle-of-the-night readings); an alert to let you know that the reading is complete (or that the unit is positioned correctly) and an auto shut-off feature to preserve battery life.
Features that don't matter so much? Speed (at least when you're talking about the difference of mere seconds between thermometers), the ability to take temperatures at multiple sites, e.g., a thermometer that can take oral, rectal and axillary temperatures, given that most docs recommend designating thermometers for a single use (and labeling them as "oral" or "rectal"), and the ability to take the temperature of things other than the body, e.g. bath water or a baby's bottle. The latter feels more like a party trick when the inside of your wrist will do just fine.
By and large, thermometers were typically $20 or less, with a couple of the non-contact infrared thermometers ringing in around $30 and a few outliers near the $100 mark.
Professional reviews of thermometers was hard to come by. While Consumer Reports had 10 parents each test 10 thermometers on their kids (with a total of 19 children weighing in), the children were age four and up, and no rectal thermometers were tested. Round-ups on Babble and Parenting.com didn't include many specifics or information about how any testing was done.
How We Tested
After reading thermometer reviews on sites like Consumer Reports, Parenting.com, Babble.com, as well as consumer reviews on Amazon.com and Babies "R" Us, and forums on parenting websites like The Bump, we made two children wish they had a different mother (or at least one who was not researching thermometers) and tested 13 different models.
Without a laboratory on hand, testing proved to be somewhat of a challenge. Initially, we tested each thermometer three times on a nine-month old. While it was helpful to see if each thermometer provided consistent readings, we couldn't be sure which of those readings, if any, were accurate. On the advice of Michal Chojnacky of the National Institute of Standards and Technology (NIST), we tried to perform an ice melting point test where the thermometers should have all read 32°F, if accurate. However, we couldn't get the thermometers to read such low temperatures (for most of them, their range was 95°F to 105°F), so for our particular needs, that test was a failure. Another possible means of thermometer calibration suggested by Chojnacky was to let water come to room temperature and measure that as compared to the thermometers in our test sample. Unfortunately, once we started questioning the accuracy of thermometers, we realized that there weren't any that we could trust without a doubt to measure the water, compounded by the fact that once again, room temperature water would have been out of the range of our sample thermometers.
Luckily, a very kind four-year-old agreed to submit himself to testing (rectal thermometers included). He remained lying down and still throughout the testing, so as to minimize any changes in body temperature. We measured his rectal temperature using a mercury thermometer for four minutes at the beginning and again at the end of the testing session and got the same reading both times (97.4°F). In between those readings, we took his temperature three times with each sample thermometer.
Although we considered the mercury thermometer a likely reliable means of comparison, we were unsure of when it had been calibrated last, so as a final step in testing, we tried to test the accuracy of the thermometers by boiling water and then testing the thermometers as the water neared 100°F as it cooled, as measured by an infrared thermometer provided by another editor. (The IR thermometer measured the surface temperature of the water, while our thermometers measured the temperature of the water about ¼- to ½-inch below the surface—which had been stirred immediately prior to measuring, in order to minimize any differences in temperature throughout the water.) Michal Chojnacky of the NIST cautioned that infrared thermometers may be less reliable than others for this type of measurement because, "It's very difficult to get a reproducible measurement because of the color, how shiny the target is... You're going to get a different answer. [Infrared] thermometers have a very specific use for high temperatures like melting steel where you can't use a contact thermometer."
Despite not having access to the certainty of testing a laboratory would provide, we were able to come to some conclusions. For example, we found that some thermometers were more accurate (at least when compared to the mercury thermometer and the infrared thermometer used for comparison) and more consistent than others. We also determined that the most basic models were often the easiest to use because they were straightforward and didn't require scrolling through different options while trying to soothe a fussy baby.
After several rounds of testing, we found that the Safety 1st Gentle Read Rectal Thermometer performed the best. Its simple design (shaped to prevent over-insertion, with a single On/Off button) made it very easy to use, and when compared to the mercury thermometer, it provided accurate and consistent readings (97.8°F, 97.7°F, and 97.8°F as compared to 97.4°F read by the mercury thermometer). It also provided speedy results (within eight seconds). Unfortunately, we were informed that the manufacturer is discontinuing this model, so we returned to our test results and chose the runner-up, the Safety 1st Advanced Solutions High Speed Rectal Thermometer.
The Safety 1st Advanced Solutions High Speed Rectal Thermometer gave consistent readings within a degree of the mercury thermometer (96.7°F, 96.6°F, and 96.7°F as compared to 97.4°F read by the mercury thermometer). It also gave us results quickly (within five seconds). Like the Safety 1st Gentle Read thermometer, it is designed to prevent over-insertion into the rectum and has a "comfort tip," making the short probe flexible and therefore less uncomfortable for baby. It also has a simple On/Off button, making it intuitive to use (which is especially helpful for those middle-of-the-night readings when you don't want to have to try to remember which button to press to get the kind of reading you need). But it also goes a bit beyond the basics, with a backlit display screen (also helpful for those late-night readings), battery indicator, and "FeverLight" bar (which lights up if your child's temperature exceeds 100.4°F). When you turn on the unit, it also displays the last temperature measurement for three seconds. It can read in Fahrenheit or Celsius (to change measurements, hold the On/Off button for five seconds). To signal a reading is complete, the thermometer will make one long beep, the back light will illuminate and a "Clean Me!" icon will blink. (Although we hope everyone already knows to clean a rectal thermometer after a reading.) To let you know that the battery (CR1632 or equivalent button battery) is dying, the battery icon will display half a battery and flash—but according to the product manual, it should still provide a minimum of 20 more measurements. The manual says that it is accurate to 0.2°F between 96°F to 107°F, and it has a measurement range of 90°F to 107°F.
Because it's part of Safety 1st's "Advanced Solutions" product line, it comes with a guide from the American Academy of Pediatrics with expert advice on fever and temperature taking and includes information about what constitutes a fever (100.4°F or higher when measured rectally or via tympanic or temporal artery thermometers; 100°F or higher when measured orally; 99°F when measured with an axillary thermometer). While not necessary per se, the information could be useful for new parents. It also comes with a one-year limited warranty. At $11 (on Amazon), we think it's worth it to invest in a rectal thermometer, even if you only use it for baby's first year.
Who Else Likes It?
At the moment, we're alone in even rating this thermometer, let alone liking it (but it's a relatively new product, only released in 2013). It currently doesn't have any reviews on Amazon.com, Target.com or Toysrus.com (Babies "R" Us).
If you'd rather go for a model that's been around for longer, we also recommend the Vicks Baby Rectal Thermometer, which has a 3.6 out of 5 stars rating from 196 reviews on Amazon, the oldest of which dates to 2005 (it's also the top selling rectal thermometer on the site). Like the Safety 1st thermometer, it is also designed to prevent over-insertion, comes with a flexible tip, and has a simple, straightforward functionality, providing a reading within 10 seconds. Some users complain of poor battery life and that it's not waterproof (but the directions state that it should not be submerged; only the sensor area of the thermometer should be washed with soap and water). A recent reviewer (October 2013) wrote, "My little one is 19 months and this thermometer has been great ...very accurate. You do not have to be concerned about using it incorrectly. I have not had problems washing mine like other moms. I typically put water and soap on tissue to wash it down really well. I highly recommend it!" In our comparison against the mercury thermometer (97.4°F), we got readings of 97.0°F, 96.4°F and 96.1°F. It comes with a lifetime warranty, which beats that of Safety 1st—and comes in handy if you'll have this around for a few years with multiple kids. According to the product manual, the battery (a long life battery; type SR41) should last for more than 200 hours of continuous operation (an upside down triangle will appear in the lower right of the display when the battery needs to be replaced). It should read within 0.2°F between 96°F and 107°F at a room temperature of 71°F, and it has a temperature range of 90.0°F to 109.9°F. Finally, it also has a backlit LCD display, like the Safety 1st model, and comes in a bit cheaper at $10.94.
The Step Up
If you truly cannot bring yourself to use a rectal thermometer, or your baby is old enough to reliably use another style of thermometer, there are other good options available.
The Exergen Temporal Scanner TAT-2000C is no doubt one of the most popular thermometers on the market today (currently the second-best selling health thermometer on Amazon)—in fact, it's one we owned personally before any of this research began. It gets a 4.0 out of 5 stars on Amazon with a whopping 486 reviews. Again, these are not currently recommended for use on babies younger than three months. Obviously, one of its main benefits is that it is non-invasive—however, we still found it challenging to use on an awake baby (although the product manual explains that if a child squirms away before a measurement has been completed, keeping the button depressed will allow you to continue the measurement without having to wait). It recommends waiting about 30 seconds in between readings to "avoid excessive cooling of the skin." The screen is now backlit (older models were not), making for easier middle-of-the-night readings. It takes a 9-volt battery, which makes replacing them easy, and comes with a one-year warranty. Unfortunately, user error is easy—lots of people swipe from the middle of the forehead down to the temple, but the directions instruct users to swipe from the center of the forehead directly across to the hairline (not down the side of the face, which can lead to falsely low readings because of how much deeper the temporal artery is there). Additionally, if your child is visibly sweaty, you won't be able to get an accurate reading—which can be a challenge if a child is especially feverish (although can take a reading behind the ear lobe as an alternative in that case). It's also more expensive than rectal thermometers at $29.
If your babe is over six months old, the Braun Thermoscan Ear Thermometer may be another good choice for you. It's the top selling ear thermometer on Amazon, with 665 reviews and 4.4 out of 5 stars. We found it easy to use, fast, accurate and consistent—just not meant for super young babies because of their small ear canals. It's a pricier choice ($40), and it requires disposable lens filters (although it comes with 21 in the box; a box of 40 will run you $5). Unfortunately, the screen isn't backlit, though—which does make middle-of-the-night temperature readings more challenging.
We considered these alternatives from manufacturers, but can't recommend them.
- Vicks V977 Forehead Thermometer — Although this was Consumer Reports' top pick, when we requested a sample for testing, we were informed that it was in limited distribution and was being phased out.
- Braun Forehead Thermometer — We had a hard time getting the timing right on this one; it requires swiping from the center of the forehead to the temple and back and we never managed to time it correctly to get it back and forth before the confirmation beep, despite numerous attempts. The instructions indicate that swiping too fast or too slow can impact the accuracy of the reading, so this one just didn't work well for us.
- Safety 1st Advanced Solutions Easy Read 4-in-1 Thermometer — Although this thermometer had an easy-to-read big screen (a plus for tired parents' eyes!), it didn't perform as well in testing as some of the others.
- Safety 1st Advanced Solutions Family Thermometer — At the start of our testing, we got several error messages. Once we were able to get a reading, the second reading was two degrees higher than the first, despite waiting just a minute in between readings, as directed in the product manual. In the comparison against the mercury thermometer, readings were consistently two degrees lower than the mercury reading. It is also a little too easy to turn it on (brushing up against just about anything made it beep and turn on). Finally, it's big and bulky and would take up more space than a thermometer should in a medicine cabinet.
- Vicks Behind Ear Gentle Touch Thermometer — Numerous online reviewers indicate that it's challenging to find the right spot behind the ear to get an accurate reading. We found this in our testing as well—especially when the nine-month-old kept turning her head toward the thermometer, thus moving its position. Finally, it gave us error messages on several occasions, despite seemingly correct positioning.
- Vicks SpeedRead Digital Thermometer — Sadly, we could never get this one to turn on. Ever. And given online user reviews with battery complaints, we weren't that surprised.
- Vicks Comfort Flex Digital Thermometer — While this particular thermometer performed relatively well for us, it would be easy to insert it too far into the rectum (and given how much babies may squirm during a rectal temperature reading, we know how easy that is to do). But it received an especially poor rating from Consumer Reports (the lowest of all tested) for accuracy and repeatability, and user reviews are pretty negative (1.8 out of 5 stars on Amazon).
- SantaMedical Non-Contact Infrared Thermometer— Gets decent reviews and performed well enough in our home testing (although aiming just a tiny bit off led to a jump of more than a degree between readings), but it's less intuitive to use and requires reading the manual a couple of times over—something no parent wants to have to do when they've got a sick kid on hand.
- VeraTemp Non-Contact Thermometer— Performed consistently and seemingly accurately in home testing, but unit shuts off so quickly that it had often turned itself off by the time we had cycled through the modes to get to "Body" (it also reads "Room" and "Surface Temp") and gotten the unit into the correct position two to three inches away from the baby's forehead, which made for a very frustrating cycle.
- The First Years American Red Cross Soothing Touch Temporal Thermometer— Numerous negative user reviews about inconsistency led us to dismiss this model.
- Graco 1 Second Ear Thermometer — Poor reviews (including mentions of it as "garbage" and "junk") left this thermometer out of the running.
- Safety 1st's Baby's 1st 3 in 1 Thermometer — Its design allows for over-insertion (despite a gauge for guidance—but that gauge doesn't actually prevent it from going in too far).
- The First Years American Red Cross 5-Second Rectal Thermometer — Negative reviews about inconsistency led us to discount this model.
- Safety 1st Digital Pacifier Thermometer — Pacifier thermometers are generally considered less accurate than other styles of thermometers, but we had hoped to give one a try for parents whose babies are paci-lovers. Unfortunately, when we requested a sample, we learned this model is being phased out.
- Thermofocus BV-1500 "5 in 1" Family Fever Thermometer — A hefty price tag ($94.99) and mixed reviews steered us clear of this model.
- A number of other basic flexible and rigid tip thermometers were excluded because of their design, e.g. this one from CVS, which was rated fairly well by Consumer Reports. Given how concerned most new parents are about inserting a thermometer too deeply (and how important doctors consider rectal temperature measurements in the very young), we wanted to stick with rectal thermometers designed with a short probe, making them impossible to insert too far.
Care, Use, Maintenance, and Repair
It should go without saying that it's important to clean rectal thermometers after use, with either rubbing alcohol or lukewarm soapy water, followed by a cool water rinse (check your individual product manual for specific instructions). Other than that, all they should require is an occasional battery change.
What To Look Forward To
If temporal artery thermometers continue to show solid results in clinical studies, medical bodies like the American Academy of Pediatrics may eventually revise their recommendations and allow for their use in infants younger than three months.
Wrapping It Up
Given the home testing we were able to do (as opposed to the laboratory testing we'd like to do), and the fact that our original top choice is being discontinued, the Safety 1st Advanced Solutions High Speed Rectal Thermometer is our current pick for the best baby thermometer from the newborn stage through infancy. Easy to use, accurate, consistent, and well-designed, we think you (and your baby) will be happy with it—at least as happy as a rectal thermometer can conceivably make a person.
- Peter Gwynne, Mercury Thermometers Face Final Phase Out, Inside Science News Service, February 25, 2011.
- Mercury Releases and Spills, U.S. Environmental Protection Agency, Last updated July 24, 2013
- Mercury Thermometer Alternatives, NIST.gov, Last updated August 7, 2012
- "Dr. Charles", What Is the Best Type of Infant Thermometer?, KevinMD.com, August 4, 2011
- Thermometers: Understand the Options, MayoClinic.com, October 23, 2012
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- Jennifer Shu, Interview, Pediatrician, author and medical editor of HealthyChildren.org, September 9, 2013
- Sam Kean, The Sort of Sad Death of the Mercury Thermometer, Slate, March 1, 2011
- Michal Chojnacky, Interview, Physicist in the Sensor Science Division of the Thermodynamic Metrology Group at the National Institute of Standards and Technology, September 11, 2013
- Video: Ice Point Calibration, National Institute of Standards and Technology, Uploaded December 13, 2012
- Carla Kemp, Temporal artery thermometers may rival rectal thermometers in ED, AAP News, Vol. 34, No. 4, April 2013
- Thermometers, Consumer Reports, Last updated April 2012
- Kate Bayless, Babble Reviews the Best Thermometers for Kids and Family, Babble.com, March 10, 2009
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- Heidi Stephens, Which Thermometer Is Best?, Chicago Tribune, February 1, 2012.
- How to Take a Child's Temperature, HealthyChildren.org, Last updated November 1, 2013
- Society of Pediatric Nurses, Position Statement for Measurement of Temperature/Fever in Children, Drafted December 2007; Approved by the Board February 2008
- Carie A. Braun, PhD,RN, Accuracy of Pacifier Thermometers in Young Children, Pediatr Nurs. 2006;32(5):413-418
- How to Buy a Thermometer, BabyCenter.com, Last updated September 2013
- Q+A: What's the Best Way to Clean a Thermometer?, Parents.com, Orignally published in the November 2008 issue of Parents magazine
Melanie Monroe Rosen is a freelance writer on the move from Brooklyn, NY to Charleston, SC. Former senior editor at Parenting.com, current mom of three, doula, and childbirth educator-to-be.
If you like this guide, find more at TheNightlight.com.