IngredientsChemical name and classification: Chlorine is a halogen with an atomic mass of 35.5 Da, with two stable isotopes, 35Cl and 37Cl. In biological and nutritional contexts, chlorine exists almost exclusively as the chloride ion (Cl−), a monovalent anion formed when the element gains one electron. Chloride (Cl−) is the predominant anion in intracellular fluid and one of the most important extracellular anions. It is not a botanical compound; it is an essential inorganic mineral and electrolyte with no plant-derived botanical name. Its chemical symbol is Cl and its ionic form, Cl−, is the biologically active species.
Natural sources and food forms: Chloride is found in table salt or sea salt as sodium chloride (NaCl). It is also found in many vegetables; foods with higher amounts of chloride include seaweed, rye, tomatoes, lettuce, celery, and olives. Chloride, combined with potassium, is also found in many foods, and potassium chloride is a common salt substitute.
Supplement and food additive forms: Chloride may be added to food as sodium chloride ("table salt") or as mixtures of sodium chloride and potassium chloride. Other chloride-containing food additives include chloride in conjunction with calcium, chromium(III), magnesium, manganese, and zinc, as well as thiamine hydrochloride and pyridoxine hydrochloride, which may be added to both food and food supplements. As a dietary supplement ingredient, common forms include potassium chloride, potassium citrate, potassium phosphate, potassium aspartate, potassium bicarbonate, and potassium gluconate. Chloride is needed to help maintain ionic and fluid balance in the body, and useful pharmaceutically acceptable chloride compounds include sodium chloride, chromium chloride, stannous chloride, and potassium chloride.
Bioavailability and absorption: In the small intestine, the elements of sodium chloride split into sodium cations and chloride anions. Chloride follows the sodium ion into intestinal cells passively, making chloride absorption quite efficient. Chloride is the primary anion in extracellular fluid. In addition to passively following sodium, chloride has its own protein channels that reside in cell membranes; these protein channels are especially abundant in the gastrointestinal tract, pancreas, and lungs.
The history of chloride as a nutrient and therapeutic agent is inseparable from the history of sodium chloride (table salt), as the two were always obtained together from natural sources and were not chemically distinguished until the early modern era.
Prehistoric and ancient use: The importance of salt dates to prehistoric times, when early humans first harvested it for its powerful preservative properties. Before the invention of refrigeration, salt was crucial for preserving meat and fish, allowing food to be stored for long periods and facilitating extensive trade across regions. This ability to preserve food made salt a symbol of wealth and a highly sought-after commodity. The term "salary" is derived from the Latin word salarium, which referred to payments made to Roman soldiers, often in the form of salt.
Ancient Egyptian medicine: Salt is mentioned as an essential ingredient in medical science in some of the oldest medical scripts. The ancient Egyptian Papyrus Smith, which is thought to refer to the famous master-builder and doctor Imhotep of the third pre-Christian millennium, recommends salt for the treatment of an infected chest wound. According to the papyri, the most common causes of salt usage in Ancient Egypt were treating wounds and mummifications (sodium chloride is well known as a putrefaction inhibitor), cure against diarrhea and dehydration, and cosmetics. In Ancient Egyptian medicine, natron's use was very similar to salt, mostly externally for wound treatments, skin curing, purification, mummification and embalming, and washing.
Roman and early medieval use: The ancient medical texts are full of recipes using sodium chloride or natrium. Current pharmacological knowledge does not fully explain its place in ancient medicine. Roman civilization extensively exploited salt for both nutritional and preservative purposes; salt also played a key role in ancient trade routes, such as the Silk Road.
19th-century medical use: Medical practitioners of the 19th century paid particular attention to the effects of natural salt. In 1860, in eastern Bavaria, a sodium chloride solution was used as a compress against inflammation. Further west, inflammations of the belly button of children were washed with salt water. The encyclopedic 18th-century literature also documented salt's therapeutic applications: the encyclopaedias of the 18th century published extensive treatises on salt, in particular rock and sea salt, and referred to current knowledge on the healing powers of salt. A particularly noted book was the work by Paulini (1734), which held a collection of remedies for diseases of all kinds; salt was a frequent ingredient.
Scientific separation of chloride from sodium: By the 19th century, scientists began distinguishing chloride as a discrete chemical entity. In 1858, Claude Bernard found that a lesion in the brain produced chloride diuresis. The formal characterization of chloride as the major extracellular anion, distinct from sodium, emerged fully only in the 20th century with the development of modern analytical chemistry and clinical laboratory measurement.
Chloride is itself the active compound — it is a monovalent anion that participates in multiple physiological processes directly, and is not a carrier for any secondary active compound.
Chloride (Cl−) is the predominant anion in intracellular fluid and one of the most important extracellular anions. It contributes to many body functions including the maintenance of osmotic and acid–base balance, muscular and nervous activity, and the movement of water and solutes between fluid compartments. Electrolytes regulate the movement of water between different compartments in the body through osmosis. Sodium and chloride primarily control fluid volume in the extracellular space (outside cells), while potassium influences intracellular fluid volume.
The chloride ion concentration in blood plasma is around 95 to 105 mEq/L. Chloride ions easily move across extracellular fluid (ECF) and intracellular fluid (ICF) through leakage channels and antiporters, maintaining anion balance in these compartments.
The most well-recognized role of Cl−, the major anion in the body, is as a counter ion to the cation for maintenance of electroneutrality. Beyond this, chloride is central to acid–base homeostasis through the chloride–bicarbonate exchanger (also known as the "chloride shift"): for every hydrogen ion secreted by the oxyntic cells there is an uptake of one molecule of carbon dioxide, and one bicarbonate ion is formed and exchanged for a chloride ion from the sodium chloride of the blood in vivo, or of the saline solution in vitro. High metabolic activity within certain tissues generates considerable amounts of carbon dioxide, which is subsequently transformed into bicarbonate in the cytoplasm of red blood cells thanks to the enzyme carbonic anhydrase. Transported via the bloodstream and reaching the lungs, bicarbonate then reverts back to CO2 — a waste product expelled during exhalation.
Chloride and hydrogen ions are secreted separately from the cytoplasm of parietal cells and mixed in the canaliculi. This creates a negative potential of between −40 and −70 mV across the gastric mucosa; gastric acid or stomach acid is the acidic component — hydrochloric acid — of gastric juice, produced by parietal cells in the gastric glands of the stomach lining. Parietal cells produce HCl by secreting hydrogen and chloride ions. When pepsinogen and hydrochloric acid exist together in the gastric juice, pepsin takes its active form. In chemical terms, gastric acid is an acid solution with a pH of 1 to 2 in the stomach lumen, consisting mainly of hydrochloric acid (HCl) (around 0.5%, or 5,000 parts per million), and large quantities of potassium chloride (KCl) and sodium chloride (NaCl).
With this higher acidity, gastric acid plays a key protective role against pathogens. It is also key in the digestion of proteins by activating digestive enzymes, which together break down the long chains of amino acids.
Beyond classical electrolyte roles, chloride acts as a direct molecular signal in the kidney: a family of serine-threonine kinases (With-No-Lysine (K), WNK) has been demonstrated to play a key role in the regulation of electrolyte homeostasis, the actions of the renin-angiotensin-aldosterone system, and the transporters upon which loop and thiazide diuretics work. Notably, chloride appears to bind directly to the catalytic site of at least two of the WNK kinases, inhibiting their auto-phosphorylation and activation. These kinases then phosphorylate highly conserved residues of major sodium transporters in the kidney such as the Na-K-2 chloride co-transporter (NKCC2) and electro-neutral sodium chloride cotransporter (NCC). NKCC2 is the target of loop diuretics and NCC the target of thiazide diuretics, transporters that mediate >25% of renal salt reabsorption.
Active Cl− transport such as Na+-K+-2Cl− transporter (NKCC) and K+-Cl− transporter (KCC) is involved in the maintenance of the membrane potential. In addition, Cl− also plays physiological roles in regulation of activities of enzymes, gene expression, ion channels, ion transporters, ion pumps, ion environments, infection prevention, and more. These include roles in GTPase activity, neurite elongation, resistance against anticancer drugs, cell death, regulation of cell volume, autophagy, cell proliferation, ciliary movements, sweet/umami taste sensing at sweet/umami taste receptors, WNK activity, epithelial Na+ transport, mRNA expression of epithelial Na+ channel (ENaC), the Na+,K+-pump activity, and pH homeostasis cooperating with bicarbonate.
The body has sophisticated mechanisms to maintain electrolyte homeostasis. The kidneys are the primary regulators, filtering blood and adjusting how much of each electrolyte is reabsorbed or excreted. Hormones like aldosterone and antidiuretic hormone help fine-tune this process by signaling the kidneys to retain or release specific electrolytes.
Chloride is classified as an essential mineral, and multiple international bodies have established intake reference values, primarily by equating chloride requirements to sodium requirements on a molar basis.
EFSA (European Food Safety Authority, 2019): The EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) has derived dietary reference values (DRVs) for chloride. There are no appropriate biomarkers of chloride status, no balance studies and no adequate evidence on the relationship between chloride intake and health outcomes that can be used to set DRVs for chloride. The Panel considered that reference values for chloride can be set at values equimolar to the reference values for sodium for all population groups, and are as follows: 1.7 g/day for children aged 1–3 years, 2.0 g/day for children aged 4–6 years, 2.6 g/day for children aged 7–10 years, 3.1 g/day for children aged 11–17 years, and 3.1 g/day for adults including pregnant and lactating women. For infants aged 7–11 months, an adequate intake of 0.3 g/day is set.
German Nutrition Society: Corresponding to the estimated value for sodium intake, the equimolar estimated value for chloride intake for adults from the age of 19 years is set to 2,300 mg/day.
MedlinePlus / U.S. National Library of Medicine: Dosages for chloride, as well as other nutrients, are provided in the Dietary Reference Intakes (DRIs) developed by the Food and Nutrition Board at the National Academies of Sciences, Engineering, and Medicine. DRI is a term for a set of reference intakes that are used to plan and assess the nutrient intakes of healthy people. The National Academies' 2005 Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate document is the primary U.S. reference.
Dietary adequacy in Western populations: Dietary chloride deficiency is rare. Sodium chloride added during industrial food processing, discretionary use, or food preservation is the major source of dietary chloride in Western diets. Most Americans probably get more chloride than they need from table salt and the salt in prepared foods.
The role of chloride in hydration has been well-characterized physiologically. When you exercise heavily or sweat profusely, you lose electrolytes, particularly sodium and chloride, which is why rehydration solutions often contain these minerals. This provides the physiological rationale for chloride's inclusion in oral rehydration solutions (ORS), sports drinks, and electrolyte supplements. However, the clinical evidence base for chloride specifically — as distinct from sodium or the combined NaCl molecule — in human hydration trials is limited, as most studies examine NaCl as a unit rather than isolating chloride's independent contribution.
This is the area where the most concentrated body of clinical research on chloride has emerged in recent years. Despite significant advances in management, heart failure continues to impose a significant epidemiologic burden. For decades, sodium has been the serum electrolyte most commonly associated with outcomes; however, challenging the conventional paradigm of sodium's influence, recent studies have identified a more prominent role for serum chloride in the pathophysiology of heart failure. More specifically, hypochloremia is associated with neurohumoral activation, diuretic resistance, and a worse prognosis in patients with heart failure.
Recent studies demonstrated that chloride is a key electrolyte for regulating plasma volume during worsening heart failure and its recovery, leading to the development of the "chloride theory" for heart failure pathophysiology and a diuretic treatment strategy by modulating the serum chloride concentration. According to the "chloride theory," dysregulated body fluid distribution can be adjusted by manipulating the serum chloride concentration using a suitable diuretic.
Specific clinical studies: A retrospective analysis using data from PhysioNet involved 1,996 patients admitted with heart failure between December 2016 and June 2019, with a composite endpoint of all-cause death or rehospitalization at 3 months. It has been demonstrated that low serum chloride levels are associated with a poor prognosis in heart failure.
The prognostic value of serum chloride has been reported primarily in patients with heart failure with reduced ejection fraction, and evidence is more limited in patients with heart failure with preserved ejection fraction (HFpEF). Patient data were extracted from the PURSUIT HFpEF study, a prospective multicentre observational registry for acute decompensated heart failure with preserved ejection fraction (ADHF-HFpEF) in Osaka. The data of 870 patients were analysed after excluding patients with in-hospital death, missing follow-up data, missing data of serum chloride level, or on chronic dialysis therapy. The primary endpoint was all-cause mortality. A significant association was observed between serum chloride level and clinical outcomes in the Japanese multicentre ADHF-HFpEF cohort.
Researchers aimed to investigate the association of baseline serum chloride with clinical outcomes in elderly patients with non-ischaemic dilated cardiomyopathy (NIDCM) in a retrospective study. A total of 1,088 patients (age ≥60 years) diagnosed with NIDCM were enrolled from January 2010 to December 2019. Logistic regression analyses showed that serum chloride was significantly associated with in-hospital death. Receiver operating characteristic (ROC) curve analyses showed that serum chloride had excellent prognostic ability for in-hospital and long-term death (AUC = 0.690 and 0.710, respectively). Kaplan-Meier survival analysis showed that patients with hypochloremia had worse prognoses than those without hypochloremia (log-rank χ² = 56.69, p < 0.001).
A study encompassing 7,063 patients with coexisting diabetes and congestive heart failure demonstrated, after rigorous adjustment for numerous potential confounding factors, a negative correlation between serum chloride levels and in-hospital mortality. The application of smooth curve fitting techniques further supported the presence of a linear relationship between serum chloride levels and in-hospital mortality.
Serum chloride levels in acute heart failure were inversely associated with loop diuretic response and were prognostic; however, changes in chloride levels were associated with parameters of decongestion, but not with clinical outcomes. This suggests, as further characterized, that persistent or incident hypochloremia was independently associated with worse survival, while hypochloremia that resolved by day 14 was not correlated with survival; this suggests that abnormalities in chronic chloride homeostasis are of far greater importance than acute perturbations.
Strength of evidence: Multiple observational and retrospective cohort studies across several countries (USA, Japan, China) consistently show an inverse association between serum chloride levels and adverse outcomes in heart failure. However, as of the time of this writing, whether or not modulating serum chloride levels, independent of serum sodium, impacts clinical outcomes is not yet certain. Randomized controlled trials directly targeting chloride to improve HF outcomes are lacking. The evidence base is observational and, therefore, cannot establish causation.
While the biological mechanisms linking dyschloremia to adverse events are still being elucidated, evidence suggests potential effects through alteration in serum pH, reduced cardiac contractility, immunosuppression, and activation of neurohormonal systems leading to excessive afferent renal artery vasoconstriction and decreased renal perfusion. Recent studies have identified hypochloremia as an independent predictor of mortality in patients with heart failure, chronic kidney disease (CKD), and critical illness.
A 2024 study evaluated chloride as a prognostic biomarker in critically ill COVID-19 patients: A total of 499 patients with a confirmed COVID-19 diagnosis by polymerase chain reaction were enrolled in the study. The serum chloride levels of patients upon hospital admission were recorded and categorized into three groups: ≤97 mmol/L for hypochloremia, 98–107 mmol/L for normochloremia, and ≥108 mmol/L for hyperchloremia. Serum chloride levels upon admission were markedly lower in tocilizumab users, patients requiring ICU care, and patients who died. The findings provide evidence supporting the value of serum chloride levels as a prognostic biomarker in critically ill COVID-19 patients.
Strength of evidence: This is a single observational study; further prospective studies are needed to confirm chloride's independent prognostic role in infectious critical illness.
The EFSA Panel notes that chloride may play a role in the effect of sodium chloride on blood pressure. Whether it is the sodium component, the chloride component, or the combination of the two in NaCl that drives blood pressure effects remains an area of ongoing scientific investigation. Most human studies have not been designed to isolate chloride's independent contribution to blood pressure, making it difficult to draw firm conclusions about chloride alone.
While not a supplementation area per se, the role of chloride channels in cystic fibrosis (CF) represents well-established, definitive clinical science directly relevant to chloride biology. Cystic fibrosis (CF) is caused by the loss of functional CFTR Cl− channels. It is not understood how this defect disrupts salt and liquid movement in the airway, but CF airway surface liquid was found to have a higher NaCl concentration than normal. In the CF sweat gland, loss or malfunction of plasma membrane CFTR results in excretion of sweat with a three- to five-fold higher sodium chloride concentration than sweat from healthy individuals. It is the failure of NaCl reabsorption across the CFTR-deficient sweat duct membrane that results in the excessively salty sweat of patients.
People with cystic fibrosis have sweat chloride values ≥60 mmol/L due to CFTR protein dysfunction. CFTR modulators improve CFTR function and decrease sweat chloride in those with responsive genetic variants. Pooled analyses from CFTR modulator studies demonstrate a relationship between measures of CFTR function in vitro and in vivo (sweat chloride), as well as consistently better outcomes among people with CF who achieve lower on-treatment sweat chloride concentrations.
Strength of evidence: The role of chloride channel dysfunction in CF is mechanistically definitive and supported by extensive clinical data, with sweat chloride now an established diagnostic and therapeutic monitoring biomarker.
Hypochloremia is associated with neurohumoral activation, diuretic resistance, and a worse prognosis in patients with heart failure. Chloride is now recognized as a key electrolyte influencing cardiorenal interactions.
Chloride plays an important role in acid-base balance, which is the body's mechanism for maintaining stable pH levels. This is particularly evident in the kidneys, where chloride ions are reabsorbed or excreted as needed to adjust pH levels in the blood. The kidneys are the primary regulators of electrolyte homeostasis, filtering blood and adjusting how much of each electrolyte is reabsorbed or excreted.
Chloride is essential for producing hydrochloric acid (HCl) in the stomach. Chloride secretion drives active intestinal secretion; these secretory processes are critical for normal gastrointestinal functions, including digestion and absorption. The protein channels for chloride are especially concentrated in the gastrointestinal tract, pancreas, and lungs.
Active Cl− transport such as Na+-K+-2Cl− transporter (NKCC) and K+-Cl− transporter (KCC) is involved in the maintenance of the membrane potential. Chloride is critical for setting the resting membrane potential in neurons and for inhibitory neurotransmission mediated by GABA and glycine receptors, which gate chloride channels.
CFTR proteins are found on the surfaces of epithelial cells in various organs in the body. Normally, CFTR protein channels transport ions, such as chloride and bicarbonate, into and out of epithelial cells in these organs. Dysregulation of epithelial chloride transport has broad consequences throughout the respiratory, gastrointestinal, and reproductive systems.
Excess chloride — hyperchloremia — arising from dehydration or severe renal failure induces acidosis. It leads to lethargy and rapid and deep breathing in patients. Normal serum range for chloride is 97 to 107 mmol/L, with levels less than 96 mmol/L defining hypochloremia. Hypochloremia can contribute to metabolic alkalosis.
Chloride is delivered as a dietary supplement primarily as a component of salts rather than as elemental chloride. The following dosages have been reported in authoritative literature:
In healthy individuals, chloride concentrations in the blood range from 96 to 106 mEq/L. Though the second most abundant electrolyte in the serum after sodium and having a fundamental role in acid-base status, chloride is less emphasized in literature and is under-evaluated.
Hypochloremia, defined as a chloride level less than 95 mEq/L, is caused by renal or extra-renal problems. Among renal causes, loop diuretic use and osmotic diuresis are the most common. The prominent extra-renal etiologies of hypochloremia are inadequate oral intake, loss of the ion via vomiting, nasogastric suction, diarrhea, skin disruption (burn), and excess water gain as in congestive heart failure.
Patients with mild hypochloremia may be asymptomatic. In significant chloride depletion and the resulting alkalosis, symptoms may include neuromuscular irritability, such as muscle cramps, twitching, and, in severe cases, seizures. Mild hypochloremia may be corrected by salt intake. For more severe hypochloremia, IV fluids may be given.
Dietary chloride deficiency is rare. Although extremely rare, inadequate dietary chloride intake is a possible cause of low chloride blood levels.
Hyperchloremia refers to an atypically high concentration of chloride in the blood, possibly triggered by factors like dehydration, excessive salt intake, ingestion of ocean water, aspirin overdose, or diseases like cystic fibrosis. Conditions causing an elevation of the serum chloride concentration and a concomitant elevation of the serum sodium concentration result primarily from disorders associated with loss of electrolyte-free fluids (pure water loss); hypotonic fluids; or administration of NaCl-containing fluids.
Too little chloride in the body can occur when the body loses a lot of fluids. This may be due to heavy sweating, vomiting, or diarrhea. Medicines such as diuretics can also cause low chloride levels. Loop diuretics (e.g., furosemide) and thiazide diuretics, both of which target chloride co-transporters in the kidney (NKCC2 and NCC respectively), are the most clinically significant medications affecting serum chloride, as their mechanism of action directly impairs renal chloride reabsorption.
Individuals who have special medical conditions associated with impaired urinary excretion of potassium (e.g., diabetes, renal failure, severe heart failure) or undergoing specific therapeutic regimens should be evaluated by their healthcare professional prior to consuming any foods or supplements containing potassium chloride.
There are no appropriate biomarkers of chloride status, no balance studies, and no adequate evidence on the relationship between chloride intake and health outcomes that can be used to set precise DRVs for chloride. Most evidence on chloride dosing in supplements is therefore derived by extrapolation from sodium balance data and equimolar calculations rather than from direct chloride-specific intervention trials. The clinical evidence on chloride as a prognostic marker in cardiovascular and critical illness settings is largely observational (retrospective cohort studies), and interventional trials targeting serum chloride directly have not yet established whether chloride manipulation independently improves clinical outcomes.
Health conditions that Chloride may help support.
Chloride, along with sodium, is the primary electrolyte lost in sweat during exercise. Depletion of chloride impairs fluid retention and electrolyte balance, which can reduce endurance performance. Oral rehydration solutions containing chloride have demonstrated superior performance preservation compared to plain water in human trials.
Chloride has an independent role in blood pressure regulation beyond its co-transport with sodium. Clinical and dietary evidence suggests the chloride component of NaCl may be more important than sodium alone in driving salt-sensitive hypertension. The sodium-chloride cotransporter (NCC) in the renal distal tubule is a key mechanistic mediator.
Chloride is the major extracellular anion and works alongside sodium to regulate fluid balance, blood volume, and blood pressure. NIH/StatPearls and MedlinePlus list it among the primary electrolytes. It is a component of hydrochloric acid in the stomach and plays a key role in acid-base homeostasis. Hypochloremia and hyperchloremia are recognized clinical electrolyte disorders.
Large sweat-induced losses of chloride (alongside sodium) are associated with exercise-associated muscle cramps (EAMC). Electrolyte-containing solutions that restore chloride and sodium reduce cramp susceptibility more effectively than plain water. American football players with sweat chloride losses above a threshold were approximately 9 times more likely to be cramp-prone.
Chloride is the major extracellular anion and, together with sodium, is the primary determinant of extracellular fluid volume. Changes in chloride homeostasis directly affect fluid distribution and retention across body compartments. This is well established in physiology and clinical medicine.
Body systems that Chloride may help support.
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