Even though I think everyone should have one, but some don't. So my question is, how can someone check their body temperature for a fever without using an oral thermometer? Is there a life hack for that?
I Do Not Have A Fever
there is not a reliable hack to measure the body temperature in a sensible way.
We have to distinguish two case where an exact body temperature may matter:
of course there a limited "hacks" that may tell us something is wrong, and we may have a fever.
So whenever we have the feeling that we may have a fever we should go and measure our body temperature with a medical thermometer. All else will not really tell us much more than what we already know: we may be ill today.
This test will be highly inaccurate because of all of the environmental factors that interfere, so try to limit them as best you can. You will need to have a freezer that freezes ice cubes at the same temperature reliably, a way to make sure ice cubes are going to have the same mass like a graduated syringe or tablespoon, a silicone ice tray to avoid chipping the cubes, and an AC unit would also help. Depending on your city, tapwater can be inconsistent with what's in it, so you might want to consider using purified water of the same brand. Don't try to measure this way after eating. Don't do this test repeatedly. If anyone can think of any other factors that may interfere, please either edit this post to add them or comment with them.
When you have a normal body temperature, take an ice cube and place it in your mouth. Without moving the ice cube around, measure how long it takes for it to disappear. This time will be your normal body temperature, so make sure to record it for later use. When you believe you have a fever, make a new set of ice cubes with the same mass. Don't try to store the same ice cubes for several days and think they're going to have the same mass. Measure how long it takes for you to melt the new ice cubes. If it takes less time, your body temperature is higher.
Keep in mind that you're putting ice in your mouth and keeping it in the same spot. Don't fill up your ice tray all the way, make the ice cube a small nugget to avoid freezer burn. Additionally, do not use this method as the way to get your temperature, use it as a fun experiment. You will have to make sure you don't have a dangerous fever with a real thermometer. You won't be able to get other peoples temperatures by comparing the time it takes for them to melt the ice cube with the time it takes for you to melt an ice cube.
I'm traveling, in a hotel, and febrile. I don't feel well enough to go buy a fever thermometer. I feel chilled and achy. I have had the heater on, every blanket on, for an hour. I assessed my neck temp with the back of my hand. I feel hot to myself. I left 80% of a steak dinner. I'm lethargic. My pulse is 75 at rest. Normally it's in the sixties. We were exposed to our grandson's snottiness nine days ago, and granddaughter's snottiness two days ago.
I'm diagnosing myself as febrile, most likely in the 100-102 *F range.
I'll test my theory by self administration of 600 mg ibuprofen. If my febrility declines, I was accurate in my assessment.
I'm a Professional Ski Patroller, Certified #580, accustomed to making do with limited resources
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I would recommend that you invest in a thermometer anyways. If you're confident that you do have a fever, though, a thermometer may be unnecessary. Do what you'd normally do for a fever, or go to a doctor. Or you could ask if someone will feel your forehead if you really would like to know, but can't get access to a thermometer.