Has anyone had good experience using an ordinary drugstore oral thermometer in the backcountry in winter weather, and getting trustworthy readings? I made the experiment (on a night that was around 30F/0C and windy and I felt subjectively chilly enough to be thinking about the possibility of hypothermia) but didn’t get readings I believed (they were implausibly low). The thermometer was digital and my assumption was the ambient air temp ruined its calibration or simply chilled the body of the device. Before I repeat the experiment with the old-fashioned glass and dyed alcohol kind, curious if people here have had practical success in measuring body temp credibly enough to actually help self-diagnose beginning stages of hypothermia.

PS thank you to the many great answers to questions elsewhere on this site regarding symptoms for diagnosing hypothermia in yourself and others.

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    While I do not necessarily disagree with the main points of the answers here, I would advise you, @mmcc , against accepting an answer so soon. Not only is it customary to give it some time for others to answer, but also, for this case I don't think your question as asked is actually answered well enough. I am curious about the actual answer to your question, as I have been wondering the same thing recently and would not mind taking rectal readings. We already do that in my family anyway when someone has a fever, so this would be no stretch for us. I recommend leaving answers unchecked for now.
    – Loduwijk
    Commented Jul 10, 2018 at 17:47
  • @Aaron noted I’ll follow site custom—I changed check box to an upvote
    – mmcc
    Commented Jul 10, 2018 at 20:05
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    You can't really self-diagnose hypothermia. Your skin can be significantly cooler than your core under normal conditions, simply sweating a lot can accomplish this. One of the first signs of hypothermia is uncontrollable shaking with the subject insisting they don't know why they're shivering so bad because they don't feel cold.
    – ShemSeger
    Commented Jul 13, 2018 at 14:38

3 Answers 3


Diagnosing hypothermia requires a special thermometer, as most over-the-counter thermometers are not accurate below 34.4 °C (93.9 °F). Additionally, local body temperature variations means you need to use a rectal, esophageal or bladder thermometer, which you probably aren't going to want to use in the wild.

Even if you had that, there is variation from person to person and day to day in their body temperature, and so the relationship between temperature and danger isn't clear.

You're better off knowing the symptoms of hypothermia and basing your decisions on what symptoms you observe.

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    I want to second this as a ski patroller and EMT in cold places -- it's much better to learn to spot the signs of hypothermia than it is to try to fiddle with a thermometer in the cold, especially since that thermometer will require stripping the patient to at least some degree. In contrast, it only takes a few seconds to see paler-than-usual skin, hear slurred words, feel a weak pulse, etc. and with a little training you can do most of it without taking off more than a couple pieces of clothes.
    – anon
    Commented Jul 10, 2018 at 21:08
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    Seconded here too. Qualatative diagnosis based on observed symptoms may not be as accurate as proper quantatative diagnosis, but it's often a lot safer in harsh environments, and it's exponentially quicker, which can be extremely important depending on what's actually wrong. Commented Jul 11, 2018 at 1:39
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    If you have a victim as cold as 34.4, you are already in serious trouble. Remember too that a hypothermia victim is often irrational and may not cooperate. (I had a kid on a trip who dumped in 3 C water and was in there for 30 minutes. We had to hold him to keep him from walking into the fire.) Warm them, feed them. Hot sweet drinks. Get them into dry clothing. Get them out of the wind. Commented Jul 31, 2018 at 19:42

This is a great question. There are many different kinds of measuring body temperature, from oral/anal digitals, temporal/infrared digitals, glass, strips, non-contact infrared, and ear thermometers.

First off, any battery-operated thermometer is useless when the batteries run out. This can happen when the batteries wear down, but it can also happen when they are cold. On the other hand, alcohol and mercury based thermometers are delicate, and the mercury ones are very accurate (if hard to come by). Also, the digitals tend to be big and bulky, and when you're looking to lighten the load on an outdoor excursion, this isn't what you want. What's more, hypothermia is a condition of the core, not of the head. So an oral thermometer of any type will not be particularly helpful. Anal thermometers are, well, not very convenient to use, and would be difficult to keep sanitary, especially for communal use.

In our group, we have adults and children (we are boy scouts), and so anal readings are categorically ruled out, but, we do keep several thermometers that can be used orally or for the armpit. We also keep oral strips on hand. We rarely use them, though.

There are stickers or paper-based ones, but, my doctor tells me they're good for measuring high temperatures, not so good for measuring low temperatures. Keep and use them if you suspect fever, that reduces need to use the more delicate thermometers, which have sanitary, breakage, and loss considerations. Also, you can keep a ton of them and they compact well and weigh less to nothing.

Having said that, if you suspect hypothermia or hyperthermia, the last thing you want to do to someone (you certainly won't be able to administer to yourself, you won't have your wits about you) is to be poking and prodding with a thermometer. If you have the slightest thought about hypo/hyperthermia, assume it has set in and then administer first aid, regardless of what any thermometer might read. As mentioned in the previous answer, knowing the symptoms is much more accurate.

In my 4 decades of camping and in marching in parades, I've overseen over a hundred cases of hypothermia or hyperthermia, and in not a single case did we worry about temperature: we just treated for it and moved on. Even in a health lodge where there are quality thermometers around to take accurate readings, we simply treated regardless. There isn't more you can do if the thermometers confirm what you already suspect, whether it is hypothermia or hyperthermia.

If you really wanted to experiment, you'll need to spend big bucks - around $1000 - and buy or borrow a Heitronics infrared thermometer, which they make scientifically accurate. This can be used to confirm what you already suspect, but the cost just isn't worth it, unless you are a doctor or a hospital where confirmation is necessary. We once treated a man for hypothermia when it turned out he was drunk. No harm in that case, but there could be other conditions - like hypo or hyperglycemia, or other conditions, which can be ruled out with expensive equipment.

But when you're in the outdoors, best to stick with knowledge and intuition, treat, and if possible, get to a doctor to rule anything else out if needed.

  • Good points. Just curious, what were the basic treatments you applied on the road for both hyperthermia and hypothermia?
    – CPHPython
    Commented Jul 11, 2018 at 9:07
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    Marching the road, hyperthermia was common, we wore heavy uniforms. For mild heat stroke, get to shade, give water, remove most clothing, apply water externally. For strong heat stroke, we did the same, but sent them to ambulance squad or fire department (we marched for both, so was easy to get them there and they can transport if needed). We never had hypothermia on the road.
    – Andrew Jay
    Commented Jul 11, 2018 at 10:53
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    I'd like to add that even proper professional thermometers can be misleading. In the check-up before blood donation I was once measured to have a severely hypothermic temp with a professional ear thermometer. I had biked there (November, Germany, cool but no necessity for a woolly knit cap), so my ears were cool outside. The measurement spot probably hit either the somewhat cool wall of the ear canal or maybe a skin flake/scale instead of the eardrum. No difficulty for the blood donation, but definitively not helpful for determining hypothermia. Commented Jul 17, 2018 at 13:51

100% no.

The best case scenario your going to get is an anal thermometer. You have to be pretty high up in management to use one of those on your self properly. Oral, infrared, or "stick on" thermometers are nearly useless unless you're trying to confirm a fever. Even then, they really only indicate "do something" and not an actual problem. Core temperature is what needs to be measured, and while there are other options an anal thermometer is the most portable.

Keep in mind that to use an anal thermometer you actually have to be bare-assed. So you may feel cold and be wondering about your situation while you are all dressed, imagine what that will mean you get out of your tent, and drop your pants down to your birthday suit and stand there, butt end up for 30 seconds or so to get the reading.

If your alone and think you may be suffering from hypothermia, the best bet is to warm your self with a low, but steady heat. Hot rocks work very well and seek immediate first aid.

If you're with others, tell them right away and seek immediate first aid.

Never use a thermometer to determine if you have hypothermia.

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