Q: Lithium, Sodium & Dehydration
I am from Chile and I was diagnosed 4 years ago. Since that I have been right
but, 1month ago I relapsed. I went to my Doctor and he told me my lythium level
was 50% lower than normal. I asked why and he said he don't know. I researched
through the internet and founded that lithium competes with sodium in
dehydration situations. I am a sportsman, I practice mountain biking, adventure
races and I am a ski instructor too. All this activities produce heavy
perspiration and in conclusion low levels of lithyum due to the competition
If that's right maybe my doctor needs more info? I take
valproic acid too and tiroid hormone. It would be so very helpful if you can
give me a response, thanks a lot.
Hola Senor Q' --
I too was a ski instructor and a sportsman. I still whitewater kayak and ski, at
areas and in the backcountry. So I understand the importance of these
activities. I also understand how much fluid loss you can have, doing those
kinds of things out there.
You are right that lithium and sodium "compete", in a
way. The same body mechanisms for handling sodium appear to also handle
lithium. As a result, when the body is trying to hang on to sodium, it will also
hang on to lithium. But here is one more bit of physiology for you that may
shift your understanding: when the body is dehydrated, it hangs on to sodium.
This creates an "osmotic" force to draw fluid in from the gut and to hang on to
any fluid the body has to spare. One of the results is a very concentrated
urine, as that osmotic force pulls back all the extra water, leaving only a
minimum to be lost (you have surely used this information on the mountain --
when you urinate and the snow is very yellow, you know you need more fluid,
So, when the body is dehydrated, it hangs on to sodium,
and thus, it will hang on to lithium as well. That's one of the ways some people
end up with "lithium toxicity": their usual lithium dose is okay as long as they
have enough water coming in. But if their water loss goes up, through sweating
during heavy physical exertion, their lithium level can go up quite a bit. If it
gets too high (e.g. 1.2 to 1.5 mEq/L or more) this can lead to vomiting, which
leads to more fluid loss and inability to keep new fluids in, leading to even
higher lithium levels; the person can get very, very sick at that point.
According to online seemingly
site, "Approximately 95% of lithium is excreted in urine, 4% in sweat...".
So, if you tripled your sweat loss, you would still overwhelmingly be
determining your lithium level with your kidneys, not your sweat.
However, if you were very careful, as an athlete like you might well be, to
replace all the fluid you lost, so that your kidneys did not perceive you as
being dehydrated, then you would not collect back so much lithium and indeed,
you could lower your blood level by losing it in sweat and not increasing kidney
reabsorbtion. How much you could lower it is not clear; seems to me you'd have
to really sweat a lot to lower it much, all the while very diligently replacing
that lost fluid (as with a Camelbak-style water supply, which many competitors
like you use routinely nowadays).
So I would not be certain you have the complete
explanation as to why your lithium level went down in your exercise and
loss of lithium through perspiration. This could also be due to different
timing of when the test was taken, or numerous other minor variables, and
generally I'd want to look at a repeat level before drawing any major
conclusions such as considering changing your dosing if otherwise things were
going well. I hope that's the case. Ski on.
Published June, 2006