Here’s the thing. Lab test every time you have extensive diarrhea/feel weak is impractical and unhelpful with what we have. Bodily K changes pretty rapidly, like everything the kidneys regulate.
Yes, I am saying exactly that a lab test for K is pointless for this before treating. For so many reasons.
Healthy kidneys means you can supplement it yourself safely with OTC hydration packets. Do you measure the lytes you consume daily? Regulate your diet precisely for micronutrients every day? No, because we don’t have to as long as kidneys work. Just like we can take multivitamins or 1000 percent of daily vitamin c without adjusting what we eat—we pee out the excess if it’s water soluble, like electrolytes and B and C vitamins.
It only becomes a risk when the kidneys are not healthy. That’s the only real lab test needed, which we all have preop before these surgeries. If that is normal and stays there, K levels at one point in time (or many) don’t help you manage a chronic problem that we know depletes K.
You don’t have to be below normal on a lab test to feel symptoms from being low in K or Mg. If you wait that long to treat, you’re letting it become dangerous. Lab levels for K reflect normal range based on cardiac risk, not the negative musculoskeletal effects and fatigue/weakness that come before you get below ‘normal’. Don’t let it come to that before you fix it.
K levels are too low in standard US diet. RDA is kept low to account for those with kidney disease and the elderly (who may not know they have kidney disease). Folate levels too low also. Vitamin D as well, though that has improved a bit lately; we don’t pee that out, but it’s hard to get to toxic levels. That’s why OTC supps w 2000 IU are available and safe for healthy people, even w RDA of 400 IU (and most of us are deficient as a result of such a low target).
Sodium is too high in American diet, by contrast. But we survive if gut is normal and kidneys are, bc they hold onto all the k and let out the extra na. Our diseased guts let the k spill, though, and na, and mg. Basic gut physiology of diarrhea. We just eat a lot more sodium normally, so we don’t often have hyponatremia except when the diarrhea is really bad. We are low in K and Mg a lot faster, bc so much less in diet to begin with. Can’t afford to lose what we do ingest.
Docs often recommend Gatorade for diarrhea, which is unfortunately sugary and has lots of sodium but minimal or no K. Not helpful. A group of athletes is selling some better versions with higher K and Mg bc that is what is needed (Body Armor—compare electrolyte levels and sugar to Gatorade or Powerade; BA is better). Even those are not enough if diarrhea is chronic, though.
The packets I use have about 17 pct of recommended daily K. Not at all dangerous w normal kidneys. I actually take an additional med that helps me retain more of it, and double the packets, but that’s because I know that’s what it takes to feel better. Never been high on labs for K unless the sample was hemolyzed (ruined by shearing of rbcs during the draw, which falsely elevates K)... I eat a ton of green leafy vegetables, too, but I don’t worry—kidneys are taking care of it, should I ever be so fortunate as to achieve ‘excess’ K consumption. Drinking the supplement has another benefit—the liter of water you mix it with will ensure the kidneys get well flushed.
But I do understand why what I’m saying seems odd to you. I had to study all of this for years before ever getting sick in the first place. This knowledge, thoughtfully applied, has kept me out of the ER for ten years of illness, and let me survive long days while doing surgeries, many long and very delicate, for eight of them.
That’s why I post on this site about stuff like this; none of my surgeons or GI docs had anything better than Gatorade to suggest for home, bc we don’t learn to read product labels in med school or residency. Their job is to reconstruct and medicate and manage pouchitis and all that hard stuff, which is plenty to master; as patients, we are often left with the day to day challenges. I had to supplement my training with reading labels to find what I needed to help mitigate the fatigue and depleted feeling, the cramps, all of it.
Anyway, huge difference between ordinary dehydration (for which Gatorade or water is usually fine) and diarrhea-induced dehydration, which comes with significant electrolyte wasting, much more than through sweating. There are a lot of things like this that we treat presumptively because it’s more logical to do so. You’ll see ‘hydration packets’ at Costco and the drugstore now that were not sold ten years ago; the best ones have more K and Mg, less Na and sugar. It’s widely sold because it’s considered safe for public consumption, as long as kidneys are normal. There’s a warning label for renal disease, but safe for the rest of us, no labs required.
In the end you have to decide what you can handle mentally as far as what you can do on your own. It is entirely safe to use these things yourself, as long as your kidneys are fine. Lab work won’t tell you why you feel weak unless you’re well beyond symptoms, in dangerous territory.
My surgeon (Remzi) always gave me extra K in hospital, even if I was technically normal on daily labs; he wanted to ‘tank me up’ for the diarrhea losses, tried to get me to at least 4.5 before discharge so I’d have a bit longer before feeling lousy. But normal is 3.3-3.5 depending on the lab standard; he just knew to aim a lot higher because this is what he does, day in and out, as an IBD surgeon and pouch specialist. I don’t think you’ll get that in an ER or regular doctor’s office if it isn’t their specialty. They’re just going to see ‘normal’ or ‘abnormal’ and not understand what to treat and why, until it’s way late.
Oh, and I absolutely hate getting blood drawn when I’m depleted. Veins go into hiding, very likely to have sheared cells from the difficult draw, and thus a serum K that looks higher than it really is, from hemolysis. A complete waste.
Sorry for the long reply. I just want to be clear that this is not empiricism run rampant. The funny thing in medicine is that we learn over time what the limitations of tests are, and we learn to use them less, esp. where they aren’t going to change management. The less providers know, the more tests they order; it’s sad but true, demonstrated in studies. And patients usually think more tests are better, bc they’re supposed to be ‘definite’, when that isn’t actually true much of the time. This is one of those times.