Written by Dr Katie Stephens, GP
Dr Katie graduated from the University of Manchester in 2007 (MBChB) and completed her GP training in the West Midlands in 2012 (MRCGP).
As part of our series on remote monitoring (checking your own health data at home instead of your healthcare professional checking it for you in person), this article is going to look at the benefits of checking body temperature specifically.
Could this be an infection?
While there are multiple different reasons for your body temperature to rise, one of the more common reasons is in response to an infection. For those interested in the physiology, this can happen both as a direct response to the offending germ (be it virus, bacteria, or other!), or as a side effect of other parts of the immune system becoming activated. When using an in-ear thermometer in an adult, a ‘low grade fever’, or slightly raised temperature is considered to be 37.5 – 37.9°C. A ‘proper fever’ is 38°C and above.
While having a fever may seem concerning, in the context of an infection, it can actually be a good thing in and of itself. It can make it harder for whatever is infecting us to grow and multiply1, and may also make our own immune system even more efficient at fighting back2.
Sometimes it is easy to know if you have a fever. You might find yourself shivering, or having to throw off the bedcovers as you are suddenly sweating. Or your child might feel burning hot to the touch. At these points, using a thermometer is only really confirming what you know already.
At other times though, you may just feel a bit warmer or colder than usual, or just as though something is vaguely a bit off. Or, if your child is perhaps feeling a little warm but doesn’t have the verbal skills to tell you how they are feeling, or you have a loved one who generally has difficulty expressing themselves verbally, it can be helpful to have a tool to tell you whether their temperature is alright or not.
When should we be worried about a high temperature?
If we check with a thermometer and see that there is in fact a fever present, this can then alert us to pay closer attention to how we or our loved ones are coping with this infection. Of course, it should also prompt a COVID-19 test, where appropriate3. Symptoms that should prompt urgent medical attention in someone who has a fever would include:
- A temperature of 38°C or higher in babies under 3 months old, or 39°C or higher in babies age 3-6 months.
- Feeling lethargic, lightheaded or confused (or in children, a lack of interest in their toys, or difficulty waking them from sleep)
- Feeling more short of breath than normal
- A rash that doesn’t fade when applying pressure (the ‘glass test’)
- Fever in combination with a headache and any of the following: visual disturbances, vomiting, neck stiffness, or difficulty tolerating bright lights
- Being dehydrated (a sign of this is dark urine or knowing you’ve not drunk enough or fewer wet nappies in young children)
- Looking very pale, or skin looking mottled or blue
- Fever lasting 5 days or longer
- Having that gut feeling that something is not right
Depending on which symptoms are present, it would be appropriate to reach out to your NHS GP or 111, or even to ring 999 for the more severe symptoms (eg new rash that doesn’t fade, severe headache, severe breathing difficulties or extreme drowsiness). For further information, see the NHS page on advice for fever in children4 or in adults5. Of course, even in the absence of a fever, if you are concerned that you or your child are unwell, don’t let the absence of a raised temperature stop you from seeking appropriate medical advice.
Can temperature predict ovulation?
There are of course, other reasons for wanting to monitor one’s temperature. Women who are planning to conceive may find temperature tracking a helpful tool in mapping out their cycles and thereby predicting any extra-fertile windows. Alongside other things to monitor, checking body temperature helps as we know that this goes up a little after ovulating.
Somewhat similarly (but with the opposite intent!), ‘natural family planning’ involves tracking cycles and ovulation in order to predict when ovulation will occur and then avoid intercourse at times when it could result in pregnancy (typically 7 days prior to ovulation and 2 days after). An alternative is using additional contraception, such as condoms, during this time. This is a very precise process that normally requires training prior to implementation, and generally would involve the use of digital thermometer with increased accuracy as the temperature changes involved are only slight.
So, there are just a couple of examples of why it might be useful to monitor your temperature at home. If you do decide to purchase a thermometer, please ensure it is clinically validated, like all of Kinetik’s are, so you know you can rely on the reading you get.
- Small PM, Täuber MG, Hackbarth CJ, Sande MA. Influence of body temperature on bacterial growth rates in experimental pneumococcal meningitis in rabbits. Infect Immun. 1986 May;52(2):484-7. doi: 10.1128/iai.52.2.484-487.1986. PMID: 3699893; PMCID: PMC261024. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC261024/
- Rice P, Martin E, He JR, Frank M, DeTolla L, Hester L, O’Neill T, Manka C, Benjamin I, Nagarsekar A, Singh I, Hasday JD. Febrile-range hyperthermia augments neutrophil accumulation and enhances lung injury in experimental gram-negative bacterial pneumonia. J Immunol. 2005 Mar 15;174(6):3676-85. doi: 10.4049/jimmunol.174.6.3676. PMID: 15749906. https://www.jimmunol.org/content/174/6/3676.long