What is chloride?
Table salt is sodium chloride, and in your body those two stay together. Sodium is the positive particle that attracts water and determines your fluid balance; chloride is the negative particle that keeps it company. If sodium rises because you are dehydrating, chloride rises along; if sodium falls through dilution, chloride falls along. On its own chloride is therefore often an echo of sodium. But chloride has a second job. Your blood has to stay electrically neutral, so opposite the positive particles there is always a fixed amount of negative ones. Chloride and bicarbonate are the two largest of those, and they complement each other like communicating vessels: if bicarbonate disappears, chloride shifts up to fill the gap, and the other way round. Bicarbonate is the buffer that protects your blood against acidification, and so chloride takes part in acidity. If you vomit stomach acid, which is full of chloride, the kidney holds on to bicarbonate and chloride falls; if you have acid to spare through diarrhoea or kidney damage, chloride rises to replace the lost bicarbonate. Your report shows chloride in mmol/L. Normal is about 101 to 108 mmol/L, where the labs overlap. The value usually sits in a row with sodium, potassium and bicarbonate, and that row is where you read it.
Why is chloride relevant?
Chloride is rarely the value you wait for, and that is the honest message of this page. It is almost always measured together with sodium and potassium because it comes from the same test, and in most cases it confirms what sodium already says: both up is dehydration, both down is dilution. Anyone who is healthy and sees a chloride within the band need do nothing with it. Where chloride does add something is when it moves independently of sodium, because then the story is not about water but about acid. A low chloride with a normal sodium fits persistent vomiting, diuretics or a body holding on to too much carbon dioxide through a lung disease, and goes with a high bicarbonate. A high chloride with a normal sodium fits long-lasting diarrhoea, kidneys that cannot get rid of acid well or a drip with a lot of salt, and goes with a low bicarbonate. That pattern, chloride against bicarbonate, is what a doctor uses to see which way the acid-base balance has tipped. For anyone who does a lot of sport or works in the heat, chloride is like sodium a measure of what has gone with the sweat. Sweat is salt water, and anyone who sweats for hours and drinks back only water sees sodium and chloride fall together. That is not a chloride problem but a water problem, and the solution is the same as with sodium: drinking to thirst, with salt alongside if it lasts long.
Chloride reference ranges
What counts beside the number:
- Sodium from the same draw: if the two move together, it is about water
- Bicarbonate: if chloride and bicarbonate move against each other, it is about acid
- Whether you have vomited, had diarrhoea or take diuretics
- How much you have sweated and drunk, certainly around a long effort
- Potassium and creatinine, which say whether the kidneys are involved
- Which lab processed your test, because around a hundred the lower bound differs per lab
There is no national reference value for chloride, so the band of your own lab is the only one that counts, and around a hundred it differs per lab. More important than the band is the row chloride sits in: if it moves with sodium, it is about water; if it moves against bicarbonate, it is about acid.
What Dutch labs actually use
Chloride is the value three of the four labs agree on exactly: Unilabs, Star-shl and Certe all hold 97 to 108 mmol/L. Clinical Diagnostics stands alone with 101 to 109 and thus sets its floor four units higher. A value between 97 and 101 mmol/L is simply normal at three labs and called low at the fourth.
101 – 108mmol/L
Between 97 and 101 and between 108 and 109 it depends on the lab, because each sets its limits on its own method and population. Above 109 every lab calls it abnormal.
every lab calls 101 – 108 mmol/L normal. Between 97 and 101 and between 108 and 109 it depends on the lab.
Every age, per lab
| Laboratory | Group | Reference range |
|---|---|---|
| Unilabs(Saltro, Medlon, SHO, Atalmedial)2026 | All ages | 97–108 mmol/L |
| Star-shl2026 | All ages | 97–108 mmol/L |
| Certe2026 | From 4 months | 97–108 mmol/L |
| Clinical Diagnostics2026 | All ages | 101–109 mmol/L |
Each band as the lab publishes it, retrieved in 2026, unless marked otherwise.
Chloride high or low: what it means
A low chloride means loss or dilution. In order of how often it occurs: loss of stomach acid through persistent vomiting, or through a stomach tube; diuretics, which make the kidneys release chloride and hold on to bicarbonate; and dilution through too much water, in which sodium falls along. If sodium moves along, it is about water; if sodium stays normal and bicarbonate is high, it is about acid and vomiting or the diuretic is the explanation. A high chloride usually means concentrating. With dehydration from fever, diarrhoea, heat or drinking too little, sodium and chloride rise together, and that recovers with water. If chloride rises while sodium stays normal and bicarbonate is low, the body is losing bicarbonate or cannot release acid: with long-lasting diarrhoea, with advanced kidney damage or after a drip with a lot of salt. That is a pattern to look at together with creatinine and bicarbonate. What you do about it: nothing to chloride itself, but to the reason. With dilution or concentrating, water is the lever, with salt alongside during a long effort. With vomiting or diarrhoea the value recovers as soon as that stops and you drink back salt and water. With diuretics it is a conversation with whoever prescribed them. With kidney damage chloride belongs to the values a kidney specialist follows, and then bicarbonate is the value that is topped up where needed. Always read chloride beside sodium, because moving together means water, beside bicarbonate, because moving against each other means acid, and beside potassium and creatinine, which say whether the kidneys are involved.
What lowers it
Loss of chloride, or dilution in which sodium falls along.
| Cause | How often |
|---|---|
| Loss through the gastrointestinal tractStomach acid is full of chloride; with persistent vomiting or a stomach tube you lose it, and bicarbonate rises at the same time | Often |
| Diuretic medicationDiuretics make the kidneys release chloride and hold on to bicarbonate; the value falls while sodium often stays normal | Sometimes |
| Too much water during long exertionSweat carries salt away and drinking back only water dilutes the rest; chloride and sodium then fall together | Sometimes |
What raises it
Almost always together with something else, and that other thing decides what it means.
| Cause | How often |
|---|---|
| Concentrating through fluid lossChloride and sodium move up together, because there is less water to dissolve them in; water restores it | Often |
| Heavy fluid loss through diarrhoeaWith gut fluid you lose bicarbonate, and chloride rises to fill the gap | Sometimes |
| Advanced chronic kidney diseaseThe kidneys cannot get rid of acid well; bicarbonate falls and chloride rises, and creatinine and the eGFR show the kidney | Sometimes |
How does a chloride blood test work?
- Referral
- Not needed. Chloride comes from the same test as sodium and potassium and often comes along automatically; you can have it measured yourself.
- Fasting
- Not needed; what you eat hardly shifts the chloride in your blood.
- When
- Not straight after a long effort or a day in the heat, and not during vomiting or diarrhoea, unless you want to know exactly how your salt and acid balance stands at that moment.
- The draw
- One tube of blood from a vein in your arm. Sodium, potassium, bicarbonate and creatinine come from the same draw, and without those three chloride says little.
- Repeating
- Only if sodium or bicarbonate deviate too, within days to weeks beside those two. In a healthy body chloride comes along with every blood test by itself.
- Where to draw
- You can draw at 250+ locations near you, no referral needed. See the locations
Frequently asked questions
What is chloride?
The negatively charged particle from table salt, which follows sodium everywhere in your body. It also has a second job: your blood has to stay electrically neutral, and chloride and bicarbonate are the two largest negative particles that regulate that together. If bicarbonate disappears, chloride shifts up to fill the gap, and the other way round. So chloride takes part in the acidity of your blood.
What is a normal chloride value?
Between 101 and 108 mmol/L, where the four labs overlap; three labs already start at 97. There is no national band, so around a hundred your own lab decides whether a value is called normal or low. What you eat hardly shifts the value; what shifts it is water, vomiting, diarrhoea, diuretics or acid.
What does a high chloride mean?
Usually concentrating. With dehydration from fever, diarrhoea, heat or drinking too little, sodium and chloride rise together, and water restores that. If chloride rises while sodium stays normal and bicarbonate is low, the body is losing bicarbonate or cannot release acid: with long-lasting diarrhoea, advanced kidney damage or after a drip with a lot of salt. You read that pattern beside creatinine and bicarbonate.
What does a low chloride mean?
Loss or dilution. Persistent vomiting makes you lose stomach acid and with it chloride, diuretics make the kidneys release chloride, and too much water during a long effort dilutes chloride and sodium together. If sodium falls along, it is about water; if sodium stays normal and bicarbonate is high, it is about acid and vomiting or the diuretic is the explanation.
Why do you read chloride beside bicarbonate?
Because the two work like communicating vessels. Bicarbonate is the buffer that protects your blood against acidification, and chloride fills in what bicarbonate leaves behind. A high chloride with a low bicarbonate means acid to spare, through diarrhoea or kidneys that cannot get rid of acid; a low chloride with a high bicarbonate means acid lost, through vomiting or diuretics. Sodium meanwhile says whether something is also up with the water.
What does chloride have to do with sweating?
Sweat is salt water, and anyone who sweats for hours and drinks back only water sees sodium and chloride fall together. That is not a chloride problem but a water problem: there is too much water for the salt that is left. Drinking to thirst, and with an effort longer than a few hours salt or a sports drink alongside, keeps both values up.
How do I get my chloride back to normal?
By tackling the reason; there is nothing to do to chloride itself. With dilution or concentrating, water is the lever, with salt alongside during a long effort. With vomiting or diarrhoea the value recovers as soon as that stops and you drink back salt and water. With diuretics it is a conversation with whoever prescribed them. With kidney damage a kidney specialist follows the value beside bicarbonate, which is topped up where needed.
Why is chloride on my report when I did not ask for it?
Because it comes from the same test as sodium and potassium, and most labs send it along automatically. On its own it adds little in a healthy body. It only becomes interesting when sodium or bicarbonate deviate too, because then chloride shows whether the story is about water or about acid.
Which tests include chloride?
Chloride is part of Advanced, the broader panel. It is not orderable yet.
Related biomarkers
Sources
- 1.Unilabs, test catalogue (Dutch): chloride. 2026. bepalingenklapper.nl
- 2.Star-shl, test catalogue (Dutch): chloride. 2026. star-shl.nl
- 3.Certe, test catalogue (Dutch): chloride. 2026. bepalingenwijzer.certe.nl
- 4.Clinical Diagnostics, lab guide (Dutch): chloride. 2026. clinicaldiagnostics.nl
- 5.Khanna and Kurtzman, Metabolic alkalosis, Respiratory Care 46(4). 2001. pubmed.ncbi.nlm.nih.gov
- 6.Adeva-Andany et al., Sodium bicarbonate therapy in patients with metabolic acidosis, The Scientific World Journal. 2014. pubmed.ncbi.nlm.nih.gov
Educational information only, not medical advice. Consult a healthcare professional for clinical decisions.
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Chloride is part of Advanced, the broader panel. It is not orderable yet.
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