I just got back some of my lab results today. I've felt for a long time that I am not salt sensitive, so I basically eat what I want in terms of sodium. Can one tell anything of any consequence from one's serum sodium? I see mine was 140 with a reference range of 135-148.
When taking HCTZ my sodium readings are always consistently low, as low as 127 early in April. I then drank wine like a crazed wino for 3 weeks and got a 135 which is about as high as it goes.
I KNOW I am extrememly salt sensitive and I also drink a huge amount of liquids, mostly water, diet lemonade, and coffee so I jusge my endlessly low sodium as something of a "water intoxocation" problem. I should test when I am thirsty sometime and see what I get.
My docotr says lower the HCTZ but then he add to try some horrible drug or another...usually amlodipine, until I AGAIN remind him that I cough from ACEI's, ARB's have almost ZERO effect on me, beta-blockers are good drugs only for those with angina or heart failure and Norvasc should only be given to animals...to euthanize them.
Next blood test, I'll go in and tell him I STOPPED EVERYTHING. If we go off on an endless tangent I will add "and that everything includes YOU."
So, I think that one's serum sodium most reflects the amount of water consumed during the day before and maybe the overall condition of the kidneys. I'm beginning to think I should have a closer look at mine; I shouldn't be so salt sensitive and water retentive. Either that or I have frown SERIOUSLY addicted to thiazide.
I don't think one can judge one's BP salt sensitivity from serum sodium levels. Probably the best way would be some sort of standardized test measuring BP response to a certain size "sodium insult"...say 2 hours after 4 grams of ingested sodium (and all the water you want) or some such...or a pound bag of Amish pretzels washed down with diet Pepsi!:!
I've been having the blood tests done now for about 40 years and sodium was usually on there, but since it never was out of range, I had not given it much thought before. I did fear that what you said about giving no clue about salt sensitivity might be the case. But I was hoping.
I've tried in the past to get some idea of salt sensitivity by testing my BP before and after a high salt meal, but it was never an extremely high salt meal. And with my very volatile BP, I suppose I'd either have to do like you say, have an enormous amount of salt, or compare BP results after high-salt and low-salt meals several times. The question occurred to me yesterday, though, because after a particularly low-sodium lunch, my BP went UP! With my volatile BP, though, I do suspect the sodium probably had nothing to do with it.
I don't notice any change in my blood pressure from eating a lot of salt, but I can put on 2 or 3 pounds in a day from lots of salt. I don't know if this has always happened to me though. Since I have been dieting and trying to keep my weight down I watch my calories more carefully, and since I am on Depo Provera I only have periods once every 3 months, so the monthly cyclic bloat is controlled. I also weigh myself every day now where there was a long time I didn't have a scale. It will take a day, maybe two to get rid of that extra water. If I get really nervous about a day after eating a lot of salt, I flush it and the water out pretty quickly!
Good point about the water retention. I haven't noticed any water retention problems in over 20 years. No particular indentation from wearing an elastic waistband, for example, so I really doubt that I'm salt sensitive. Nonetheless, I think I'll still do a little sodium-load test one of these days and maybe, just maybe, I can convince my doctor not to keep reminding me to restrict sodium. I think I'll wait, though, until I buy a new digital scale. My mechanical scale is about 40 years old, and just isn't accurate enough for something like this. It gives a good enough approximation of weight for most purposes, though, so it has served me well all these years.