Chloride is an essential element in the blood that plays an important role in acid and electrolyte balance, kidney and muscle function, and transport of minerals, water, and gases. Keep reading to learn more about the chloride blood test and normal electrolyte and chloride levels.
What Is Chloride (Cl-)?
Chloride is an essential electrolyte (a mineral that conducts electricity when in water). Chloride is the body’s main anion (negatively charged electrolyte) and represents 70% of the total negative electrolytes [1, 2].
Along with other electrolytes, chloride helps maintain [2, 3]:
- A healthy mineral concentration, acid level, and electrical balance of the body fluids
- Fluid and mineral movement between cellular compartments
- Acid production in the stomach
- Kidney function
- Muscular activity
- Blood pressure
- Transport of oxygen and carbon dioxide by red blood cells
The average adult consumes 5.8-11.8 g chloride a day from salt [2].
Chloride is mainly excreted through the kidneys into the urine (although 99.1% is reabsorbed), dependent on the body requirements and chloride intake [4, 2].
What Is the Chloride Blood Test?
Chloride levels are usually measured with a blood test, which is done as part of an electrolyte or metabolic panel. It can also be measured via sweat, serum, urine, and feces, in certain circumstances. The test measures the concentration of free chloride and the results are shown in milliequivalents of chloride per liter of blood (mEq/L) [2, 5].
Lab results are commonly shown as a set of values known as a “reference range”, which is sometimes referred to as a “normal range”. A reference range includes the upper and lower limits of a lab test based on a group of otherwise healthy people.
Your healthcare provider will compare your lab test results with reference values to see if your chloride results fall outside the range of expected values. By doing so, you and your healthcare provider can gain clues to help identify possible conditions or diseases.
Remember that some lab-to-lab variability occurs due to differences in equipment, techniques, and chemicals used. Don’t panic if your result is slightly out of range – as long as it’s in the normal range based on the laboratory that did the testing, your value is normal.
However, it’s important to remember that a normal test doesn’t mean a particular medical condition is absent. Your doctor will interpret your results in conjunction with your medical history and other test results.
And remember that a single test isn’t enough to make a diagnosis. Your doctor will interpret this test, taking into account your medical history and other tests. A result that is slightly low/high may not be of medical significance, as this test often varies from day to day and from person to person.
Normal Chloride Levels
The normal ranges for chloride levels are [1]:
- Premature babies: 95-110 mEq
- Full-term babies: 96-106 mEq
- Children and adults: 95-105 mEq
Low chloride levels (<95-100 mEq/L) are referred to as hypochloremia, while high levels (>106-110 mEq/L) are known as hyperchloremia. It is important to note that certain conditions can interfere with the analyses and result in artificially high or low chloride levels [1].
For instance, if the blood contains excess solid material (excess triglycerides or plasma cell cancer), it can interfere with the electrode, incorrectly registering as lower chloride levels [6, 7].
Conversely, electrolytes like iodide and bromide or drugs like salicylate can be incorrectly picked up by the electrode and register as higher chloride levels (such as in case of poisoning) [8, 9, 10].
Normal Electrolyte Levels
To maintain blood as an electrically neutral fluid, the concentration of positively charged electrolytes (sodium, potassium, calcium, and magnesium) must equal the concentration of negatively charged electrolytes (chloride, bicarbonate, phosphate, sulfate, and organic electrolytes) [11].
Only sodium, potassium, chloride, and bicarbonate are normally measured in blood tests. The difference between non-measured negative and positive electrolytes is called “anion gap” and is used for quality control, and to diagnose acid-base disorders, excess of antibodies in the blood (paraproteinemia), and poisoning with lithium, bromide, and iodide [12, 13, 14, 15, 8].
Normal concentrations of the main electrolytes inside the cells (left) and in blood (right). Source: [16].
Effect of Drugs on Chloride Levels
1) Carbonic Anhydrase Blockers
Carbonic anhydrase II transforms carbon dioxide into bicarbonate. Blocking this enzyme increases chloride accumulation to compensate for the reduction of negative electrolytes. The main blockers are [17]:
- Acetazolamide (used for glaucoma, epilepsy, pressure around the brain, and altitude sickness)
- Methazolamide (used for glaucoma and pressure in the eyes)
- Ethoxzolamide (used for glaucoma, ulcers in the bowel, and as a diuretic)
- Dichlorphenamide (used for glaucoma and as a diuretic)
- Dorzolamide (used for glaucoma and pressure in the eyes)
- Brinzolamide (used for glaucoma and pressure in the eyes)
- Zonisamide (used for epilepsy and Parkinson’s disease)
Some inhibitors of the enzymes that produce prostaglandins during inflammation also inhibit carbonic anhydrase II. Among them, the main ones are [18]:
- Celecoxib (arthritis and menstruation and acute pain)
- Valdecoxib (arthritis and menstruation pain)
- Rofecoxib (arthritis and menstruation pain)
2) Diuretics
Loop diuretics are drugs acting on a certain region of kidney cells (loop of Henle), where they block the Na+/K+/2Cl- cotransporter. As a result, they reduce the reabsorption of sodium, potassium, and chloride in the kidneys. The main ones are [19]:
- Furosemide
- Bumetanide
- Ethacrynic acid
- Torsemide
Thiazides and thiazide-like diuretics increase water elimination by blocking the Na+/Cl- cotransporter, which prevents the absorption of sodium and chloride in the kidneys. The most common ones are [20, 21]:
- Hydrochlorothiazide
- Bendroflumethiazide
- Metolazone
- Chlorthalidone
- Clopamide
- Xipamide
Potassium-sparing diuretics are drugs that increase the elimination of water, sodium, and chloride through the kidneys without causing potassium losses. The main ones are [22]:
- Aldosterone blockers like spironolactone and eplerenone: they prevent the binding of aldosterone (a hormone triggering the production of electrolyte transporters) to its receptor [23].
- Sodium channel blockers like amiloride and triamterene: they directly block sodium absorption channels, thus causing a reduced absorption of sodium and chloride [24].
3) Corticosteroids
Aldosterone is a hormone that promotes sodium and chloride absorption. Corticosteroid drugs such as cortisone and hydrocortisone bind to the aldosterone receptor and also activate the absorption of these electrolytes [25, 2].
However, the long-term use of corticosteroid drugs causes a condition called Cushing’s syndrome in which the glands above the kidneys are damaged and the production of aldosterone and other corticosteroid hormones stops. This causes the loss of sodium and chloride [26, 27].
4) Laxatives
The laxative lubiprostone turns on the chloride channel ClC-2, which secretes chloride to induce the entry of sodium and water into the bowel. Similarly, an herbal laxative (anthraquinone) turns on the chloride secretion channel CFTR [28, 29].
Limitations and Caveats
Although the studies covered in this post were mainly human studies, a large number of them were retrospective cohort studies. Because these studies look at existing data, the data may be inaccurate, incomplete, or inconsistently measured. Thus, most of the data collected is only correlational (shows a relationship between the factors) and not causal (determines a cause and effect) [30].
Takeaway
Chloride is an essential electrolyte that helps maintain normal blood pressure, acid-base balance, oxygen transport, and mineral levels in the body. It can be measured with a blood test, typically as part of an electrolyte or metabolic panel.
Normal chloride levels in children and adults are 95-105 mEq. Values below this range are considered low (also known as hypochloremia) and values above it considered high (hyperchloremia).
The anion gap is usually used to estimate the blood levels of other electrolytes and diagnose acid-base disorders.
