Lab result explainedMetabolic panelLast updated November 1, 2026

Chloride blood test: what high and low chloride levels mean

Chloride (Cl) · Comprehensive metabolic panel (CMP) / Basic metabolic panel (BMP) / Electrolyte panel · reported in mEq/L (same as mmol/L)

Chloride is the main negatively charged electrolyte in your blood, where it works alongside sodium to control fluid balance and alongside bicarbonate to keep blood acidity steady. Most labs call 96 to 106 mEq/L normal (some print 98 to 107). The two most common reasons it reads high are dehydration and a bicarbonate-losing process such as diarrhea or kidney disease; the two most common reasons it reads low are vomiting and diuretic medicines.

On its own chloride rarely tells a story. It moves with sodium, so a high chloride with a high sodium usually means water loss, and a low chloride with a low sodium usually means water excess or salt loss. When chloride moves in the opposite direction to bicarbonate, the clue is an acid-base problem: chloride goes up as bicarbonate goes down and vice versa. That is why a chloride result is always read next to sodium, CO2 and the anion gap.

Most isolated chloride results a point or two outside the range are not worrying and are repeated with the next panel. This page explains what the number measures, what drives it up or down, how clinicians tell a harmless shift from a real one, and the lifestyle factors that influence it.

Cl at a glance

What it is: the main negative electrolyte in blood, paired with sodium for fluid balance and with bicarbonate for acid-base balance.
Normal: about 96 to 106 mEq/L (mmol/L); ranges vary slightly by lab.
High chloride (hyperchloremia): dehydration, large volumes of normal saline, diarrhea, kidney disease, renal tubular acidosis, hyperventilation, or drugs such as acetazolamide.
Low chloride (hypochloremia): vomiting, nasogastric suction, loop or thiazide diuretics, heart failure, chronic lung disease (CO2 retention), Addison's disease or excess water.
It is read with sodium and CO2: chloride moving opposite to bicarbonate signals an acid-base disturbance.
Next step: repeat with a full electrolyte panel; treat the cause (fluids, stopping a drug, replacing losses) rather than the number.

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What Cl measures

Chloride comes almost entirely from salt (sodium chloride) in food. It is absorbed in the gut, circulates in the blood and the fluid around cells, and is filtered and reabsorbed by the kidneys in tandem with sodium. The kidney fine-tunes chloride to balance the body's total negative charge: when bicarbonate rises, chloride falls, and when bicarbonate falls, chloride rises, so that the sum of negative ions matches the positive ones.

The lab measures chloride in serum or plasma with an ion-selective electrode and reports it in mEq/L, which equals mmol/L. The same analyser produces sodium, potassium and CO2, and from these the anion gap is calculated: sodium minus the sum of chloride and bicarbonate. A normal gap (about 8 to 12) with a high chloride and low bicarbonate points to a 'hyperchloremic' metabolic acidosis from the gut or kidney tubules.

Chloride is also measured in sweat (the diagnostic test for cystic fibrosis) and in urine, where a low value helps confirm that a low blood chloride is due to vomiting. Those are different tests from the blood chloride on a metabolic panel.

Normal range for Cl

Reference ranges vary between labs and by age, sex and pregnancy. Use the range printed on your own report.

Group	Typical range (mEq/L (same as mmol/L))	Notes
Adults	96–106 mEq/L	Some labs use 98–107 or 97–108.
Children	98–107 mEq/L	Pediatric ranges differ slightly by age.
Newborns	96–110 mEq/L
Pregnancy	Often 1–3 mEq/L lower than non-pregnant adults	Mild dilution and slight respiratory alkalosis.
High altitude	Often at the upper end	Faster breathing lowers CO2 and bicarbonate, so chloride rises to compensate.

High chloride (hyperchloremia)

A high chloride, above about 106 to 108 mEq/L, means either the body has lost water relative to salt, has been given a lot of chloride (most often as intravenous normal saline), or is retaining chloride to replace lost bicarbonate. The sodium and bicarbonate on the same panel sort these out quickly.

If sodium is also high, the problem is water loss: dehydration, diabetes insipidus, or not drinking enough. If sodium is normal and bicarbonate is low, the problem is a normal anion gap metabolic acidosis: diarrhea, renal tubular acidosis, early kidney disease, or acetazolamide. If bicarbonate is low because you are breathing fast (anxiety, altitude, pregnancy, lung disease), chloride rises to compensate for a respiratory alkalosis.

Mild hyperchloremia from saline infusions in hospital is very common and usually resolves within a day or two as the kidneys excrete the excess. Persistent hyperchloremia with low bicarbonate deserves a kidney work-up.

Common causes

Dehydration
Losing water through sweat, fever, poor intake or osmotic diuresis concentrates both sodium and chloride. The BUN/creatinine ratio is usually raised as well.
Intravenous normal saline
0.9 percent saline contains 154 mEq/L of chloride, far above the blood level. Large volumes in hospital raise chloride and can lower bicarbonate, a hyperchloremic acidosis that balanced fluids avoid.
Diarrhea
Intestinal fluid is rich in bicarbonate. Losing it leaves the kidney retaining chloride to keep the charge balance, producing a normal anion gap metabolic acidosis.
Kidney disease and renal tubular acidosis
When the tubules cannot excrete acid or hold on to bicarbonate, chloride rises in its place. This is common in moderate CKD and in the inherited or drug-induced tubular acidoses.
Respiratory alkalosis
Hyperventilation from anxiety, pain, pregnancy, high altitude, sepsis or lung disease lowers CO2. The kidney then dumps bicarbonate and retains chloride over hours to days.
Medicines
Acetazolamide and topiramate block bicarbonate reabsorption; ammonium chloride, high-dose salt tablets and some older sulfonylureas add chloride; corticosteroids can raise sodium and chloride through water retention patterns.
Hyperparathyroidism
Excess parathyroid hormone reduces bicarbonate reabsorption by the kidney, nudging chloride up; a chloride-to-phosphate ratio above 33 was a classic clue.
Diabetes insipidus
Loss of large volumes of dilute urine raises sodium and chloride together; thirst is intense.
Lab artefact: bromide or salicylate
Bromide (in some sedatives and pyridostigmine bromide) and very high salicylate levels register as chloride on some electrodes, giving a falsely high reading.

Symptoms that can go with it

Often none when mild
Thirst, dry mouth and reduced urine output if dehydrated
Rapid, deep breathing if acidosis is present
Fatigue, weakness or muscle twitching
Confusion or irritability with a high sodium

Low chloride (hypochloremia)

A low chloride, below about 96 mEq/L, means chloride has been lost from the body, water has diluted it, or the kidney is retaining bicarbonate and letting chloride go. The most common single cause in outpatients is a diuretic; in hospital it is vomiting or nasogastric suction.

If sodium is low too, think dilution: heart failure, cirrhosis, SIADH, or drinking a great deal of water. If sodium is normal and bicarbonate is high, think metabolic alkalosis from vomiting, diuretics or steroid excess. If bicarbonate is high because the lungs retain CO2 (COPD, sleep apnea, obesity hypoventilation), the kidney raises bicarbonate to compensate and chloride falls.

A low chloride matters most in heart failure, where it is an independent marker of poor outcomes, and in anyone with severe vomiting, where it signals significant fluid and acid loss that needs replacement.

Common causes

Loop and thiazide diuretics
Furosemide, bumetanide, hydrochlorothiazide and chlorthalidone block chloride reabsorption in the kidney tubule, so chloride leaves in the urine along with sodium and water.
Vomiting or nasogastric suction
Stomach acid is hydrochloric acid. Losing it removes chloride and leaves bicarbonate behind, producing a metabolic alkalosis with a low urine chloride.
Heart failure
Fluid overload dilutes chloride and diuretic treatment removes more. A chloride under 96 in heart failure is associated with higher mortality independent of sodium.
Chronic lung disease with CO2 retention
In COPD, obesity hypoventilation or severe sleep apnea, CO2 builds up. The kidney compensates by holding bicarbonate and excreting chloride.
SIADH and excess water
Inappropriate antidiuretic hormone from lung disease, brain injury or drugs such as SSRIs retains water and dilutes sodium and chloride together.
Addison's disease
Lack of aldosterone means the kidney wastes sodium and chloride; potassium is typically high and blood pressure low.
Cystic fibrosis and heavy sweating
Sweat contains chloride, and in cystic fibrosis far more. Prolonged sweating in heat with only water replacement can lower chloride.
Excess alkali or hyperaldosteronism
Baking soda, large doses of antacids, or aldosterone excess raise bicarbonate, and chloride falls to balance the charge.
Burns and severe metabolic alkalosis of any cause
Large fluid shifts and alkali retention both push chloride down.

Symptoms that can go with it

Often none when mild
Fatigue, muscle cramps or twitching
Shallow or slow breathing if alkalosis is marked
Dizziness or low blood pressure from fluid loss
Confusion or irritability with a low sodium
Swelling and breathlessness if heart failure is the cause

Read it alongside

Sodium — chloride normally tracks sodium; when both move together the issue is water balance, when they diverge the issue is acid-base.
CO2 (bicarbonate) — chloride and bicarbonate move in opposite directions in most acid-base disorders; high chloride with low bicarbonate is hyperchloremic acidosis, low chloride with high bicarbonate is metabolic alkalosis.
Anion gap — calculated from sodium, chloride and bicarbonate; a normal gap acidosis points to diarrhea or the kidney tubules, a high gap to ketones, lactate, kidney failure or toxins.
Potassium — low potassium with low chloride and high bicarbonate is the classic vomiting or diuretic pattern; high potassium with low chloride suggests Addison's disease.
BUN and creatinine — a raised BUN/creatinine ratio supports dehydration as the reason for a high chloride.
Urine chloride — below 20 mEq/L in vomiting, above 40 with diuretics or aldosterone excess; it is the test that separates the causes of alkalosis.

What usually happens next

A chloride a few points outside the range with normal sodium and bicarbonate is usually just repeated with the next metabolic panel.
Your clinician will look at sodium, CO2 and the anion gap on the same report to classify the pattern before ordering anything else.
Expect questions about diuretics, antacids, baking soda, salt tablets, acetazolamide or topiramate, recent vomiting or diarrhea, and how much water you drink.
A persistent high chloride with low bicarbonate leads to a urinalysis with urine pH, a check of kidney function and sometimes a renal tubular acidosis work-up.
A persistent low chloride with high bicarbonate may prompt a urine chloride, potassium and sometimes aldosterone and cortisol tests.
If heart failure or chronic lung disease is known, a low chloride is a reason to review diuretic doses and breathing, not to take chloride supplements.

Diet, lifestyle and natural levers with evidence

What can move Cl once the cause is known. Nothing here replaces finding the cause.

Match fluids to losses with oral rehydration

Strong evidence

During diarrhea or vomiting, replacing water, sodium, chloride and potassium together corrects both high-chloride (diarrhea) and low-chloride (vomiting) states far better than plain water. WHO-formula oral rehydration solution has reduced deaths from diarrheal dehydration by an estimated 50 percent or more worldwide, and the same principle applies to adults recovering from a stomach bug.

People with heart failure or kidney disease should check volumes with their clinician.

Moderate salt intake

Moderate evidence

Dietary chloride comes almost entirely from salt. Reducing sodium to under 2 g a day lowers blood pressure by 4 to 6 mmHg in trials and modestly lowers chloride load on the kidney. Very high salt intake, salt tablets and heavily salted broths are a recognised cause of a creeping chloride in people with reduced kidney function.

People on high-dose diuretics or with heavy sweating can need more salt, not less; do not restrict salt if your chloride is already low without advice.

Fruit, vegetables and potassium-rich foods

Moderate evidence

Plant foods supply bicarbonate precursors (citrate, malate) and potassium. In randomised trials in CKD with low bicarbonate, 2 to 4 cups of fruit and vegetables daily corrected acidosis as well as sodium bicarbonate tablets, which lets chloride drift back down. Dietary potassium also limits the potassium loss that drives diuretic-related alkalosis.

With an eGFR below 30 or on potassium-sparing drugs, check potassium before increasing intake.

Review antacids, baking soda and supplements

Moderate evidence

Regular baking soda for heartburn, large doses of calcium carbonate antacids, or milk-alkali patterns raise bicarbonate and lower chloride; stopping them normalises both within days. Equally, ammonium chloride and salt tablets push chloride up. Many abnormal chloride results in otherwise healthy people trace back to an over-the-counter product.

Treat sleep apnea and breathing problems

Moderate evidence

Chronic CO2 retention from untreated sleep apnea, obesity hypoventilation or COPD drives a compensatory high bicarbonate and low chloride. CPAP and pulmonary rehabilitation improve daytime CO2 in trials, and the chloride follows. A low chloride with a raised bicarbonate in someone who snores and is sleepy during the day is a reason to ask about a sleep study.

When to see a clinician promptly

A chloride above 115 or below 90 mEq/L, or any abnormal chloride together with a sodium above 150 or below 130.
Persistent vomiting or diarrhea for more than 24 to 48 hours, inability to keep fluids down, or signs of dehydration such as dizziness, very dark urine or confusion.
Rapid deep breathing, drowsiness or confusion with a high chloride and low bicarbonate, which can mean significant acidosis.
Muscle cramps, twitching, weakness or an irregular heartbeat with a low chloride, especially on diuretics.
Known heart failure with a falling chloride, worsening swelling or breathlessness.
A high chloride with low bicarbonate and a rising creatinine, which can indicate kidney disease that needs evaluation.

Frequently asked questions

What is chloride in a blood test?

Chloride is an electrolyte, a mineral that carries an electric charge, and it is the main negatively charged one in your blood. It comes from salt in food and is regulated by the kidneys. On a metabolic panel it is measured alongside sodium, potassium and CO2 to assess fluid balance, kidney function and the acid-base state of the blood.

What is a normal chloride level?

Most labs report 96 to 106 mEq/L (mmol/L) for adults, with some using 98 to 107. Children run slightly higher and pregnant women slightly lower. A value one or two points outside the range with normal sodium and bicarbonate is usually not significant.

What causes high chloride levels?

The usual causes are dehydration, large volumes of intravenous normal saline, diarrhea, kidney disease or renal tubular acidosis, and hyperventilation. Drugs such as acetazolamide, topiramate and salt tablets also raise it. Clinicians use the sodium and bicarbonate on the same panel to tell which applies.

Is a chloride of 108 bad?

A chloride of 108 is only slightly above most ranges and is usually harmless, often reflecting mild dehydration, a salty diet or recent IV fluids. If the bicarbonate is normal and you feel well, it is typically just rechecked. It deserves more attention if bicarbonate is low, creatinine is up, or it keeps climbing on repeat tests.

What causes low chloride?

Diuretics, vomiting, heart failure, chronic lung disease with CO2 retention, SIADH, Addison's disease and overuse of antacids or baking soda are the main causes. Low chloride often appears with a high bicarbonate (metabolic alkalosis) or with a low sodium (dilution). The cause, not the chloride itself, is what gets treated.

Can dehydration raise chloride?

Yes. Losing water through sweat, fever, poor intake or high urine output concentrates chloride and sodium together. The BUN/creatinine ratio is usually raised as well. Rehydrating with fluid that contains some salt, rather than plain water alone, brings both back to normal.

Does a high chloride mean kidney disease?

Not necessarily. Most high chloride results come from dehydration, saline or diarrhea. Kidney disease becomes more likely when the high chloride is paired with a low bicarbonate and a raised creatinine or a low eGFR, which suggests the tubules are no longer excreting acid normally. In that case a urinalysis and kidney work-up follow.

References

Chloride Blood Test. MedlinePlus, US National Library of MedicineView source
Electrolytes. MedlinePlus, US National Library of MedicineView source
Overview of Acid-Base Maps and Compensatory Mechanisms. Merck Manual Professional Version
Metabolic Alkalosis. Merck Manual Professional Version
Hyperchloremia. StatPearls, National Center for Biotechnology Information (2023)
Semler MW, Self WH, Wanderer JP, et al.. Balanced Crystalloids versus Saline in Critically Ill Adults. New England Journal of Medicine (2018)View source
Grodin JL, Simon J, Hachamovitch R, et al.. Prognostic Role of Serum Chloride Levels in Acute Decompensated Heart Failure. Journal of the American College of Cardiology (2015)
Goraya N, Simoni J, Jo CH, Wesson DE. A comparison of treating metabolic acidosis in CKD stage 4 hypertensive kidney disease with fruits and vegetables or sodium bicarbonate. Clinical Journal of the American Society of Nephrology (2013)
He FJ, Li J, Macgregor GA. Effect of longer-term modest salt reduction on blood pressure. Cochrane Database of Systematic Reviews (2013)
Oral rehydration salts (ORS): a new reduced osmolarity formulation. World Health OrganizationView source
Hyponatremia: Diagnosis and Management. American Family Physician (2015)

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This page is educational and is not medical advice or a diagnosis. Lab results have to be interpreted together with your history, symptoms and other results by a clinician who knows you. Do not start or stop a supplement to change a lab value before the cause is known.