It’s day three of your new low-carb diet. You’re doing everything right — hitting your macros, staying disciplined, drinking plenty of water. And yet you feel terrible. Brain fog, muscle cramps, a headache that won’t quit, and a vague dizzy spell every time you stand up too fast. You Google “keto flu” and find a thousand posts telling you to push through it.

Here’s the truth: there is no “keto flu.” What you’re experiencing is an electrolyte deficiency — specifically sodium and potassium — triggered by the fact that low-carb diets cause your kidneys to excrete sodium at a dramatically higher rate. Drink more water without replacing electrolytes and you actually make it worse, because you’re diluting what little you have left.

But this isn’t just a keto problem. Most people’s electrolyte intake is quietly terrible, and the conventional advice around sodium has been more wrong than right for decades. The sports drink industry has spent billions convincing you that you need their sugar-laden products after a 30-minute jog. You don’t. This guide breaks down the three electrolytes that actually matter, why the standard narrative is backwards, and how to fix it for about 15 cents a day.

The Three That Matter: Sodium, Potassium, Magnesium

Technically, calcium, chloride, phosphorus, and bicarbonate are also electrolytes. But when people talk about “electrolyte balance” in the context of supplementation, performance, and daily health, three dominate the conversation — because three are the ones most people get wrong.

Sodium — The One You’re Told to Fear

Sodium is the primary extracellular electrolyte. It regulates fluid balance, blood pressure, nerve impulse transmission, and muscle contraction. Every time a neuron fires or a muscle fiber contracts, sodium channels are doing the work. It’s also the primary electrolyte lost in sweat — not potassium, not magnesium, sodium. A liter of sweat contains roughly 800–1,500mg of sodium but only about 200mg of potassium. When you’re drenched after a hard workout, the mineral you’re mostly losing is salt.

The Adequate Intake set by the National Academies is 1,500mg/day, with an upper limit of 2,300mg/day for the general population. Most Americans consume 3,400mg/day on average — well above the guideline. But here’s where it gets interesting: the evidence for universal sodium restriction is far weaker than most people assume.

Potassium — The One Nobody Gets Enough Of

Potassium is sodium’s intracellular counterpart. It’s critical for heart rhythm, muscle function, and nerve signaling. The Adequate Intake is 4,700mg per day for adults — and according to NHANES data, 97% of Americans don’t meet that target. That’s not a typo. Virtually no one gets enough potassium from diet alone.

The average American intake is around 2,500mg — roughly half what it should be. You’d need to eat 7–8 bananas or 4 large avocados per day to hit the AI from food. Nobody does that. The irony is that most people worry about sodium while being catastrophically low in potassium.

Magnesium — The Silent Deficiency

The third pillar. Magnesium is involved in over 300 enzymatic reactions and is essential for energy production, DNA synthesis, muscle relaxation, and nervous system regulation. We’ve written extensively about magnesium deficiency in our magnesium deficiency guide, but the short version: roughly 50% of Americans are subclinically deficient, and it’s the most common electrolyte deficit after potassium. Our magnesium supplement roundup covers form selection in detail.

The Sodium Controversy: Why “Salt Is Bad” Is Oversimplified

For fifty years, public health messaging has been unequivocal: eat less salt. The logic seems straightforward — sodium raises blood pressure, high blood pressure causes heart disease, therefore less sodium means less heart disease. But the actual evidence is far more nuanced than the soundbite.

A 2011 Cochrane systematic review (Graudal et al., Cochrane Database of Systematic Reviews) analyzed 167 studies on sodium reduction and concluded that while reducing sodium modestly lowers blood pressure in hypertensive individuals, there was no strong evidence that sodium reduction decreased all-cause mortality or cardiovascular events in people with normal blood pressure. The review explicitly noted that low-sodium diets activated the renin-angiotensin-aldosterone system and increased triglycerides and catecholamines — hormonal changes that could offset the blood pressure benefit.

Then came the PURE study (Mente et al., 2014, The New England Journal of Medicine), which followed over 100,000 participants across 17 countries and found a J-shaped relationship between sodium intake and cardiovascular events. The lowest risk was in the range of 3,000–6,000mg of sodium per day — well above the 2,300mg upper limit recommended by the AHA. Both very low and very high sodium intakes were associated with increased mortality.

What does this mean practically? If you’re sedentary, eating processed food, have hypertension, and don’t exercise, the standard advice to cut sodium probably still applies. But if you exercise regularly, eat mostly whole foods, do low-carb or keto, fast, or live in a hot climate — you almost certainly need more sodium than the guidelines suggest, not less.

The Ratio Matters More Than the Absolutes

This is the piece most people miss. It’s not just about how much sodium or potassium you consume individually — it’s about the sodium-to-potassium ratio. A 2014 meta-analysis published in the British Medical Journal (Aburto et al., originally 2013, WHO-commissioned review) found that higher potassium intake was associated with a 24% lower risk of stroke and significantly lower blood pressure, independent of sodium intake.

The ideal dietary sodium-to-potassium ratio is roughly 1:2. Most Americans eat closer to 2:1 — double the sodium, half the potassium. The fix isn’t necessarily to slash sodium; it’s to dramatically increase potassium while keeping sodium appropriate for your activity level.

Who Actually Needs Electrolyte Supplements

Here’s the uncomfortable truth the electrolyte industry doesn’t want you to hear: most people don’t need electrolyte supplements. If you eat a normal diet, do moderate exercise, and aren’t on a restricted eating pattern, food covers you. The people who genuinely benefit fall into specific categories:

Intense Exercisers and Athletes

A moderately intense 60-minute workout can produce 0.5–1.5 liters of sweat. That’s 400–2,250mg of sodium lost in a single session, plus potassium and magnesium. If you train hard for over an hour, especially in heat, targeted electrolyte replacement makes a real difference. The American College of Sports Medicine recommends 300–600mg sodium per hour during prolonged exercise. Our pre-workout protocol guide covers how to time electrolytes around training.

Low-Carb and Keto Dieters

When carbohydrate intake drops below roughly 50g/day, insulin levels fall significantly. Insulin signals your kidneys to retain sodium — so when insulin drops, your kidneys start dumping sodium at an accelerated rate. This is why the first 5–7 pounds lost on keto is almost entirely water weight — your body is shedding fluid because it can’t hold onto sodium.

Volek & Phinney, in The Art and Science of Low Carbohydrate Living (2011), recommended that ketogenic dieters consume 3,000–5,000mg of sodium, 1,000–3,500mg of potassium, and 300–500mg of magnesium daily — far above standard dietary guidelines. Most keto “failures” in the first two weeks are electrolyte failures, not willpower failures.

People Who Fast

Intermittent fasting (16:8, OMAD) and extended fasting accelerate electrolyte depletion through the same insulin mechanism as keto, compounded by the simple fact that you’re not eating. Supplementing sodium, potassium, and magnesium during fasting windows makes extended fasts dramatically more comfortable and safer.

Heavy Sweaters and Hot-Climate Residents

Individual sweat rates and sodium concentrations vary enormously. Some people lose twice the sodium per liter of sweat as others. If your workout clothes have white salt lines after a session, you are a heavy sodium sweater and need more replacement than average.

The “8 Glasses of Water” Myth and Overhydration

The advice to drink eight glasses (64oz) of water per day has no scientific basis. It was traced back by Heinz Valtin in a 2002 American Journal of Physiology review to a misinterpretation of a 1945 National Research Council recommendation that included water from food. Yet it persists as gospel.

The real danger here isn’t dehydration — it’s overhydration diluting your electrolytes. Exercise-associated hyponatremia (dangerously low blood sodium from drinking too much water) hospitalizes marathon runners every year. A 2015 consensus statement in the Clinical Journal of Sport Medicine (Hew-Butler et al.) recommended drinking to thirst rather than forcing a fixed volume — your body’s thirst mechanism is more reliable than any formula.

Commercial Electrolyte Products: An Honest Assessment

The electrolyte drink market is enormous and mostly terrible. Let’s look at what’s actually in these products and evaluate them on what matters: adequate electrolyte doses, minimal sugar, and whether they address all three key minerals.

Gatorade (20oz): 270mg sodium, 75mg potassium, 0mg magnesium, 34g sugar. That’s a tablespoon of salt dissolved in sugar water. The sodium is token, the potassium is negligible, and the sugar negates most of the hydration benefit.

Liquid I.V.: 500mg sodium, 370mg potassium, 0mg magnesium, 11g sugar. Better sodium, but still sugar-dependent and missing magnesium entirely. Uses Cellular Transport Technology (CTT), which is essentially oral rehydration therapy — a real concept, but not unique to their product.

Drip Drop (ORS): 330mg sodium, 185mg potassium, 39mg magnesium, 7g sugar. Developed by a doctor, based on WHO oral rehydration science. The most medically credible option, but the electrolyte doses are still modest for heavy exercise or keto use.

LMNT: 1,000mg sodium, 200mg potassium, 60mg magnesium, 0g sugar. This is closer to what active people actually need. The sodium is high enough to be meaningful, the potassium and magnesium are present (though supplementary, not replacements for dietary intake), and there’s no sugar undermining the effect.

The criteria that matter: does it provide at least 500mg sodium per serving, does it include all three electrolytes, and is it low or zero sugar? Most products fail on at least one of those.

The DIY Electrolyte Recipe

You can make a perfectly effective electrolyte drink for pennies. Here’s the formula:

1/2 teaspoon table salt (roughly 1,150mg sodium)
1/4 teaspoon NoSalt® or NuSalt® (potassium chloride — roughly 650mg potassium)
1/4 teaspoon magnesium citrate powder (roughly 75mg elemental magnesium)
Juice of 1/2 lemon or lime (for flavor and a small potassium contribution)
16–32oz water

Cost per serving: roughly $0.10–$0.15, compared to $1.50+ for a Liquid I.V. packet or $2.00+ for LMNT. Adjust the salt up or down based on your taste and activity level. If the salt taste is too aggressive at first, use more water and sip over a longer period.

One caveat: potassium chloride (NoSalt®) has a distinctly metallic, bitter taste. The lemon juice helps mask it, but don’t expect this to taste like a sports drink. It’s functional, not delicious.

Timing Your Electrolytes

How you time electrolyte intake matters more than most people realize:

First thing in the morning: you wake up mildly dehydrated after 7–8 hours without fluid. A glass of electrolyte water before coffee sets a better baseline than plain water, which can dilute already-depleted levels.
30–60 minutes before exercise: pre-loading sodium improves plasma volume and delays the onset of exercise-induced hyponatremia.
During long sessions (90+ minutes): sipping an electrolyte drink throughout extended training prevents progressive performance decline from sodium depletion.
During fasting windows: spread your electrolyte intake throughout the fast rather than taking it all at once. Large boluses of sodium on an empty stomach can cause nausea; steady sipping is better tolerated.

For a complete breakdown of how to schedule electrolytes alongside other supplements, see our supplement timing guide.

Signs You’re Electrolyte Deficient

Electrolyte deficiency rarely shows up on standard blood tests because your body aggressively maintains serum levels by pulling from intracellular stores and bone. By the time your blood sodium or potassium is flagged as “low,” you’re in serious trouble. Subclinical deficiency manifests through symptoms:

Muscle cramps and twitches (especially calves, feet, and eyelids) — typically magnesium and/or potassium
Headaches — often sodium, especially if they worsen with exercise or fasting
Dizziness on standing (orthostatic hypotension) — sodium depletion reducing blood volume
Heart palpitations — potassium and/or magnesium imbalance affecting cardiac rhythm
Brain fog and difficulty concentrating — all three electrolytes; neurons are exquisitely sensitive to electrolyte balance
Persistent fatigue despite adequate sleep — magnesium deficiency impairs mitochondrial energy production

If you’re experiencing several of these and you exercise regularly, eat low-carb, fast, or live in a warm climate, start with electrolytes before chasing more exotic explanations.

Cautions and Contraindications

Kidney disease: impaired kidneys cannot excrete potassium efficiently. Supplementing potassium with reduced kidney function can cause dangerous hyperkalemia. Consult your doctor before supplementing potassium if you have any kidney issues.
Heart failure or hypertension on medication: many blood pressure medications (ACE inhibitors, ARBs, potassium-sparing diuretics) affect sodium and potassium balance. Adding supplemental electrolytes requires medical supervision.
Aldosterone or adrenal disorders: conditions affecting aldosterone (Addison’s disease, primary aldosteronism) fundamentally alter sodium and potassium handling. Standard electrolyte advice does not apply.

For healthy, active people without kidney or cardiovascular conditions, the risk of harm from supplemental electrolytes at the doses described here is extremely low.

Frequently Asked Questions

Can I just add more salt to my food instead of making electrolyte drinks?

For sodium, yes — salting your food liberally is a perfectly valid strategy, especially if you eat whole foods that are naturally low in sodium. The problem is that food-based salting doesn’t address potassium or magnesium, and it doesn’t help during fasting windows when you’re not eating. If you’re active, combining generous food salting with a dedicated electrolyte drink around training covers all three bases.

Won’t all this sodium raise my blood pressure?

In salt-sensitive individuals (estimated at about 25% of the population with normal blood pressure, and about 50% of those with hypertension), excess sodium can raise blood pressure. But the PURE study data suggests that for most people, the range of 3,000–6,000mg/day carries no increased cardiovascular risk. The key variables are your activity level, how much you sweat, your potassium intake (which buffers sodium’s effect on blood pressure), and whether you have existing hypertension. If you’re concerned, monitor your blood pressure at home for a few weeks after increasing sodium intake.

Are electrolyte tablets (like Nuun) effective?

They’re convenient but usually underdosed. A single Nuun tablet provides about 300mg sodium and 150mg potassium — enough for a light walk, not enough for a serious training session or a day of fasting. Check the label for actual milligrams per serving rather than trusting marketing claims. Our label reading guide shows you exactly what to look for.

How do I know if I’m getting too many electrolytes?

Your body is remarkably good at excreting excess electrolytes through urine — assuming healthy kidney function. Signs of overconsumption include excessive thirst (paradoxically, from too much sodium), bloating, GI distress (especially from magnesium, which is osmotic at high doses), and in extreme potassium excess, irregular heartbeat. At the supplemental doses recommended here, healthy individuals are very unlikely to experience any of these.

The Bottom Line

Electrolyte balance is one of the highest-impact, lowest-cost interventions available. Most people are dramatically under-consuming potassium, about half are deficient in magnesium, and anyone who exercises, fasts, or eats low-carb likely needs more sodium than the standard guidelines suggest. But if you eat a normal mixed diet and do moderate exercise, you probably don’t need to buy expensive electrolyte packets — the sports drink industry has massively overstated the need.

If you do fall into one of the groups that benefits, start with the DIY recipe: half a teaspoon of salt, a quarter teaspoon of NoSalt®, a quarter teaspoon of magnesium citrate powder, a squeeze of lemon, and 16–32oz of water. Drink one in the morning and one around training. Give it a week. The cramps, headaches, and brain fog you’ve been blaming on stress, aging, or “keto flu” may simply disappear.

Compare electrolyte supplements in the Formulate catalog →

Electrolytes — What You Actually Need, When, and How Much