How much (electrolyte) is enough?

Just looked at the label on my Nuun “sport hydration” tablets, and the amounts supplied by each tablet look very, VERY small to me. 300mg of sodium is the only one that seems to make sense: it’s 13% DV (daily value for a 2000 kcal diet), and it’s supposed to be replacing what you’ve sweated.

But you get 1% DV of calcium, 6% DV magnesium, 2% DV chloride, and 3% DV potassium. Is that what we actually sweat out in an hour of hard exercise? Seems like tiny little amounts to me… I would think this isn’t enough even to replace what we lose, much less supplement anything.

And that got me thinking… how do we determine, or at least estimate, how much of each electrolyte we really need? What do we lose in sweat per hour (I know there are good estimates of sodium, but for the others)? What’s the best way to know if you are getting enough of all these, or to know if you’re deficient in any of them?

Seems like figuring out a supplement strategy is the easy part… the hard part is figuring what you need to supplement in the first place.

TLDR; virtually everything short of LMNT doesn’t have nearly enough sodium because if you have too much it can cause gut issues, so they err on the side of not enough (see cramping)

Let’s put it this way, I also use Nuun or Gu Tabs for electrolytes, so when using the Saturday App (@Dr_Alex_Harrison and his team for the win) I ALWAYS end up adding additional sodium. Lately I’ve backed off of the tabs to make the flavor more mild but still topped up on sodium citrate.


I use the PH1500. It’s 750 per tab.

On all the other electrolytes, I read somewhere recently that there’s really no need to address those in our drinks because we get them elsewhere (although I guess this might vary based on length of ride). I can’t remember where though. Maybe @Dr_Alex_Harrison ?


Wow, that’s a lot of salt and baking soda packed into one tab. No gut issues for you?

Well, like everything…it depends. I’ve done 80 miles of gravel in Texas heat and reached a point where I couldn’t take in anything but water, which means I cramped like I’ve never cramped before…but was that inability to eat from water, sodium, carbs, going harder and longer than I’m used to, excessive heat, humidity?

A more general answer is that I am currently doing 2-3 hours on both Sat and Sun with temps in the 100s, taking in 60-90g carbs and 750mg sodium an hour with no issues.


I think since every person is different you might have to do some of these tests. Once before exercise and once right after. Then you have numbers to shoot for.

  • Aldosterone blood test. This test looks for a specific hormone produced by your kidneys. The results can indicate certain types of electrolyte problems.
  • Aldosterone 24-hour urine test. This test also looks for aldosterone but does so using several urine samples collected during a 24-hour timeframe.
  • Anion gap blood test. The test compares the levels of specific electrolytes to see if there’s a difference between the measured levels of positive-charge and negative-charge electrolytes, which may be is a sign of certain conditions.
  • Antidiuretic hormone test (blood). This test looks for levels of antidiuretic hormone. It can help rule out certain medical conditions that share symptoms — especially excessive thirst or fluid imbalance — with electrolyte-based conditions.
  • Carbon dioxide blood test. This test measures the amount of carbon dioxide in your blood. That level can indicate if your blood is too acidic or too alkaline (basic).
  • Chloride blood test. This test analyzes a blood sample for the level of chloride found in your blood.
  • Chloride urine test. This test measures the amount of chloride in a urine sample. In some cases, it can involve several samples taken over a 24-hour period.
  • Magnesium blood test. This test analyzes levels of magnesium in your blood.
  • Blood osmolality test. This test measures the amount of certain substances in your body. It’s frequently used in cases where you’re dehydrated, overhydrated, or when poisoning is possible or suspected.
  • Urine osmolality test. This test checks fluid balance, especially with changes in how often you need to pee. Urine osmolality tests use a “clean-catch” method, which requires getting the sample in a way so that there’s no contamination from microbes that may be on your genitals.
  • Phosphorus blood test. This test measures the amount of phosphorus in your blood.
  • Phosphorus urine test. This test measures the amount of phosphorus that’s found in your urine. It may involve more than one sample taken over a 24-hour period.
  • Sodium blood test. This test measures the level of sodium in your blood.
  • Sodium urine test. This test measures the amount of sodium in your pee. It can involve multiple samples collected over a period of 24 hours.
  • Urine concentration test. This test shows healthcare providers how well your kidneys are functioning, especially their ability to manage the amount of fluid in your body. It looks specifically for the concentration of particles in your urine, electrolyte levels and particle concentration (osmolality).

When those temps go up, my desire for anything with flavor of any sort goes right out the window, so I hear you there. Heat adaptation helps, but geeze when it’s gone, it’s gone.

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Thanks for all the answers… but it seems like “trial and error” is about the best answer we have for those of us who are recreational athletes. The list of possible tests @TrekCentury listed just shows how far down the rabbit hole you could go, and of course for some highly-competitive athletes that’s the way to go.

But for average Joe Schmoe (me) who is running and biking, I can’t find an easy answer for how much supplementation of electrolytes I need…

  1. during exercise
  2. for general health

…if I need any at all. My overall diet is not great (needs more fruit and vegetables), so I’m a little concerned about #2 more than #1. But it seems to be a legitimately hard question to answer: how much is enough?

“Not great” diets often have lots of sodium in them. Maybe you don’t need to add any for general health, and can focus on your needs when riding.

It’s easy to find symptoms online of deficiencies for the usual sodium, magnesium, and potassium electrolytes. I started paying attention and being more consistent with adding sodium (and a little potassium) to my water bottles this year, and taking a daily magnesium, and so far have been feeling better after rides in the heat/humidity, and recovering much better. So I’m going to keep doing that.

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Easier to tie sodium to liter of fluid you lose/consume IMO, because rate per hour varies so much with the conditions.

I personally need around 1200mg per liter based on sweat testing.

The best way to get a stronger placebo from something that has no physiological effect is to do lots of tests beforehand and then decide on your placebo dosing, based on those tests.

This is not a joke. It legit increases placebo effect. Careful though, it can also lead to OCD. :wink:

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Sounds like the titbit (maybe an exaggeration) I read on placebo somewhere that a saline injection is a better painkiller than a sugar tablet.

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I guess it makes sense. You can talk yourself into fake pain so stands to reason you can talk yourself out of pain.

One can accidentally talk themselves into real pain.

One can accidentally talk themselves into real strength gain.

It can’t really be “talking oneself into it” as much as it’s “you intrinsically believe something and can’t be talked out of it even if someone tries.”

The belief just has to be strong enough, for some reason. That level of belief regularly causes things unexplained by typical scientific expectations. Pain happens to be one of the most common areas of this kind of very real psychophysiological manifestation.