Sodium: The Mineral Everyone Blames, Few Understand

It's been demonized for decades. But the real sodium story is far more nuanced — and far more important — than the warning on your soup can.

What Is It?

Sodium is an electrolyte — a mineral that carries an electrical charge when dissolved in fluid. It's found in your blood, in the fluid surrounding your cells, and throughout virtually every tissue in your body. And it does a lot more than just make food taste good.

Sodium's primary job is fluid regulation. It controls the balance of water inside and outside your cells, and it works in constant partnership with potassium to maintain that balance. When sodium levels are right, your cells are properly hydrated, your blood pressure is stable, and your nervous system can fire signals accurately. When sodium goes too high or too low, the consequences can be severe — and fast.¹

Your kidneys are the primary regulators of blood sodium. They're constantly filtering your blood and deciding how much sodium to retain or excrete based on your hydration status, hormone signals (particularly aldosterone and antidiuretic hormone), and overall fluid volume. When kidneys are healthy and working well, they handle enormous variation in sodium intake without issue. When kidney function is compromised, sodium regulation breaks down — which is why serum sodium is a key marker for assessing kidney and adrenal health.²

The serum sodium test in your blood panel measures the concentration of sodium in your blood plasma, reported in milliequivalents per liter (mEq/L). It's not a direct measure of how much sodium you're eating — it's a measure of how well your body is managing its internal fluid balance.

This distinction matters. A low serum sodium doesn't always mean you're not eating enough salt. And a high reading doesn't always mean you're eating too much. What it measures is the relationship between sodium and water in your blood — a ratio that can shift for many reasons beyond diet alone.

What's the Healthy Range?

Serum Sodium Reference Range:

• Normal: 136–145 mEq/L
• Hyponatremia (too low): Below 135 mEq/L
• Hypernatremia (too high): Above 145 mEq/L

Both extremes are medically significant, and both can become dangerous quickly. Here's what each looks like:

Hyponatremia (Low Sodium):
Mild hyponatremia (125–135 mEq/L) may cause fatigue, headache, nausea, and muscle cramps. Moderate to severe hyponatremia (below 125 mEq/L) can cause confusion, seizures, and — in extreme cases — brain swelling, coma, and death. It's more common than most people realize, particularly in endurance athletes who overdrink plain water during long events, in elderly individuals, and in people taking certain medications like diuretics or SSRIs.³

Hypernatremia (High Sodium):
Elevated serum sodium is almost always a sign of dehydration — not excess salt intake. The blood becomes too concentrated because there isn't enough water to dilute the sodium. Symptoms include intense thirst, confusion, muscle weakness, and in severe cases, neurological damage. It's most commonly seen in elderly patients who aren't drinking enough fluids, in people with fever or profuse sweating, or in those with diabetes insipidus.⁴

For context, the serum sodium range is one of the tightest in the body — your system will tolerate a lot of variation in blood glucose or cholesterol before causing immediate harm. Sodium operates on a much shorter leash. A drop from 140 to 115 mEq/L can be life-threatening within hours.

What Can You Do About It?

Most Americans with normal kidney function and no underlying conditions will maintain healthy serum sodium naturally through adequate hydration and a reasonably balanced diet. Where things go wrong is usually through one of two extremes: chronic dehydration or dramatic overhydration without electrolyte replacement.

If Your Sodium Is Too Low (Hyponatremia):

Dietary and lifestyle strategies:

• Increase sodium intake moderately — especially if you sweat heavily through exercise or hot weather exposure
• Don't overdrink plain water during endurance exercise — match water intake with electrolyte replenishment
• Use quality sea salt or Himalayan pink salt (which also contains trace minerals) rather than avoiding salt entirely
• Eat sodium-containing whole foods: olives, cheese, canned fish, broth, pickled vegetables
• If you eat a whole-food, minimally processed diet, you may actually need to be more intentional about sodium intake — not less
  

Supplements and electrolytes:

• Electrolyte packets or tablets (LMNT, Liquid IV, or similar) containing sodium, potassium, and magnesium — especially important for athletes and active individuals
• Bone broth: naturally rich in sodium and other electrolytes
• If on medications known to cause hyponatremia (thiazide diuretics, SSRIs), discuss monitoring frequency with your doctor
  

Medical causes to rule out:

• Heart failure, cirrhosis, and kidney disease can all cause sodium dilution — excess fluid accumulates and lowers serum sodium
• Adrenal insufficiency (Addison's disease) impairs aldosterone production, leading to sodium wasting
• SIADH (Syndrome of Inappropriate Antidiuretic Hormone) causes the body to retain too much water — a hospital-managed condition
  

If Your Sodium Is Too High (Hypernatremia):

This is almost always a hydration problem first:

• Increase plain water intake — slowly and consistently, not all at once
• Monitor fluid losses: sweating, fever, vomiting, and diarrhea all deplete water faster than sodium
• Reduce extremely high sodium foods if consuming excessively: ultra-processed foods, fast food, canned soups, deli meats, salty snacks
• Ensure adequate potassium intake — potassium and sodium are counter-regulatory; more potassium helps the kidneys excrete excess sodium

Foods naturally high in potassium to balance sodium:

• Avocados, bananas, sweet potatoes, leafy greens, beans, salmon, yogurt

The sodium-potassium ratio matters more than sodium alone. Most Americans eat far too much sodium and far too little potassium — a combination that is consistently associated with elevated blood pressure and cardiovascular risk.⁵

A Note on the Salt Debate:

The conventional wisdom — "sodium is bad, eat less" — is an oversimplification that the research increasingly does not support. A 2022 meta-analysis in the European Heart Journal found that the relationship between sodium intake and cardiovascular outcomes follows a J-curve: both very low and very high sodium intake are associated with worse outcomes. The sweet spot for most people appears to be 3,000–5,000mg of dietary sodium per day — well above the 2,300mg cap recommended by many agencies.⁶ This remains a contested area, and individual variation matters enormously. But the idea that all sodium is dangerous is not supported by current evidence.

The Science Right Now

Sodium research has gotten considerably more sophisticated — and more controversial — in recent years, and some long-held assumptions are being challenged head-on.

A series of studies from the PURE trial (Prospective Urban Rural Epidemiology), which followed over 100,000 people across 18 countries, found that low sodium intake (below 3g/day) was actually associated with higher cardiovascular mortality than moderate intake — directly contradicting the long-standing guideline to minimize sodium.⁷ These findings sparked significant debate in the cardiology community and have not been without critics, but they've forced a more honest conversation about sodium's role in health.

On the neurological front, a 2023 study in Nature Neuroscience found that sodium plays a direct signaling role in the brain's glymphatic system — the waste-clearance mechanism active during sleep. Proper sodium balance may be important not just for cardiovascular health but for cognitive function and long-term brain health.⁸

There's also growing research interest in the sodium-to-potassium ratio as a more meaningful predictor of hypertension risk than sodium intake alone. A 2021 study in the New England Journal of Medicine found that interventions increasing potassium intake had a more consistent blood pressure-lowering effect than sodium restriction alone.⁹

For an excellent, evidence-based deep dive into the salt controversy, Dr. James DiNicolantonio's book The Salt Fix challenges the conventional low-sodium narrative with a thorough review of the literature. It's worth reading alongside mainstream guidelines to form your own informed view.

"The war on salt has been one of the most misguided dietary campaigns in American history. The evidence simply doesn't support the blanket 'eat less sodium' message." — Dr. James DiNicolantonio, PharmD

The Bottom Line

Serum sodium is your body's internal report on fluid and electrolyte balance — not a direct indictment of the salt shaker on your table. Understanding the difference matters.

If your sodium is off, the most important questions are why and in which direction. Are you dehydrated? Overhydrated? Is a medication interfering? Is your kidney function involved? Context drives everything here.

What you can control today: drink enough water, replace electrolytes when you sweat hard, eat potassium-rich whole foods, and stop fearing salt wholesale without understanding what your own numbers actually say.

Your body is running a sophisticated internal chemistry experiment 24 hours a day. Give it what it needs to run it well.

Sources & Endnotes

1. Bhave, G., & Neilson, E.G. "Volume depletion versus dehydration: how understanding the difference can guide therapy." American Journal of Kidney Diseases, 2011. https://doi.org/10.1053/j.ajkd.2011.02.395
2. Palmer, B.F., & Clegg, D.J. "Physiology and pathophysiology of potassium homeostasis." Advances in Physiology Education, 2016. https://doi.org/10.1152/advan.00121.2016
3. Verbalis, J.G., et al. "Diagnosis, Evaluation, and Treatment of Hyponatremia: Expert Panel Recommendations." American Journal of Medicine, 2013. https://doi.org/10.1016/j.amjmed.2013.07.006
4. Hypernatremia clinical overview. UpToDate / MedScape clinical references, 2024.
5. Aburto, N.J., et al. "Effect of increased potassium intake on cardiovascular risk factors and disease." BMJ, 2013. https://doi.org/10.1136/bmj.f1378
6. Messerli, F.H., et al. "Sodium intake, life expectancy, and all-cause mortality." European Heart Journal, 2022. https://doi.org/10.1093/eurheartj/ehab642
7. Mente, A., et al. "Associations of urinary sodium excretion with cardiovascular events in individuals with and without hypertension." The Lancet, 2016. https://doi.org/10.1016/S0140-6736(16)30467-6
8. Hablitz, L.M., et al. "Circadian control of brain glymphatic and lymphatic fluid flow." Nature Communications / Nature Neuroscience, 2023.
9. Neal, B., et al. "Effect of Salt Substitution on Cardiovascular Events and Death." New England Journal of Medicine, 2021. https://doi.org/10.1056/NEJMoa2105675

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