Sorry, you asked about ‘possible upstream causes of electrolyte deficiency’.

In my case I believe it is caused by an undiagnosed kidney problem loosely called ‘salt-wasting syndrome’. There are many types, but they all revolve around a genetic disorder where the tubules in your kidneys that are responsible for removing different electrolytes from the urine and retaining them are malformed and are not able to keep the electrolytes like a normal kidney does. Here are a few I found in my research:

-Bartters Syndrome- https://rarediseases.org/rare-diseases/bartters-syndrome/

Many different variants, so this is a possibility. Type 5?

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-Gitelman syndrome- https://rarediseases.info.nih.gov/diseases/8547/gitelman-syn... Symptoms include tingling of face

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Fanconi Syndrome https://www.merckmanuals.com/home/kidney-and-urinary-tract-d...

I my particular case, I believe I have a type that does not impact sodium, but does potassium. When I eat a high sodium meal it causes me to pee a lot to try to get the my sodium levels back to normal. However, my body can’t retain potassium when it does this (and since I was eating much more sodium and much less potassium than my body required) I end up with normal sodium levels but low potassium levels. Taking potassium a few hours after a meal “fixed” this.

Short of genetic issue like this I am not sure what could cause it. I think this can be an early symptom of Diabetes, but don’t know much about that. What I am talking about here has got to be rare, so it may not be applicable to you.

Just another anecdote – when reading some of these links it made me remember another interesting symptom I used to have that I did not know was related: I would get “facial numbness”. Specifically, my lips and the immediate surrounding area would feel slightly numb. Usually in the morning after a poor night of sleep. I would remember feeling this on the way to work in the car. It would contribute to that dazed feeling I felt like I would swimming through a mental fog.

Oh, and one more! I also don’t get nearly so hung over from drinking! This was a surprise for me. I have always drank a lot of water while drinking alcohol, but I would always have the worst drained feeling the next day with such a headache. The headache would last all day. However, if I now take some potassium while drinking and throughout the night (depending on how much I drink), I often don’t have much of a hangover. This amazes me! I am 57 and used to drink a lot when I was in my 20’s. I had some friends that could be normal the next day and it always blew my mind. Now I think I know why. They have normal kidneys!

Higher potassium intake at dinner linked to fewer sleep disturbances – study