- 01Chloride is read through its partners
Chloride moves to balance sodium and bicarbonate. High chloride with high sodium means water loss; high chloride with low bicarbonate and a normal anion gap means bicarbonate loss; high chloride with both partners normal is usually a blip to repeat.
High chloride on a blood test points to a cause somewhere else in the body. Chloride is the main negatively charged salt in blood, and it moves to balance the two numbers printed next to it on a basic metabolic panel: sodium (positive) and bicarbonate (negative). Read on its own, a chloride of 109 mmol/L tells you very little. Read with sodium and bicarbonate, the same 109 usually points to one of three common patterns: water loss, bicarbonate loss, or a one-off blip worth repeating. Your doctor reads it with the rest of your results.
For what chloride does in the body and its full range, see the parent page on serum chloride. This page covers the high side only.
The marker this page is about
What counts as high chloride
Chloride is part of the basic and comprehensive metabolic panels and the electrolyte panel, and no fasting is needed for it 1. Modern analysers measure it with an ion-selective electrode 2. MedlinePlus gives a typical adult range of 96 to 106 mEq/L 1; some labs print 98 to 106, and each lab sets its own limits from its own analyser and population, so the flag on your report may switch on at 106, 107 or a little higher. For chloride, mmol/L and mEq/L are the same number; lab units explained covers why.
Where an example chloride of 109 mmol/L fallsmmol/L
Is my number high? Readings from 104 to 115
| Chloride (mmol/L) | Where it sits | What usually happens next |
|---|---|---|
| 104 to 105 | Normal on every common lab range | Nothing, unless bicarbonate or sodium is off |
| 106 to 107 | Top of the range; flagged high by some labs | Read with sodium and bicarbonate; usually no action |
| 108 to 110 | Mildly high on most labs | Check hydration at the draw and the companion numbers; often repeated |
| 111 to 114 | Clearly high | Needs bicarbonate, anion gap and a repeat; a cause is usually looked for |
| 115 and above | Markedly high | Get it reviewed by a clinician within a day or two, and the same day if you feel unwell or bicarbonate is also low |
Why ranges differ between labs is covered in reference ranges explained.
Read it with sodium and bicarbonate: the three patterns
Blood stays electrically neutral, with positive and negative charges in balance. Chloride makes up roughly 70% of the negative charge in the fluid outside cells, and it moves in step with sodium and opposite to bicarbonate 6. If bicarbonate falls, chloride usually rises to fill the gap. If you lose water, sodium and chloride both concentrate. That is why the pattern across three lines on the panel matters more than chloride alone.
| Pattern | Sodium | Bicarbonate | What it usually means |
|---|---|---|---|
| 1. Water loss | High or high-normal | Normal | Less water in the blood: not drinking, fever, heavy sweating, or rarely diabetes insipidus (a hormone problem that makes you pass large amounts of dilute urine) |
| 2. Bicarbonate loss | Normal | Low | Hyperchloremic metabolic acidosis (the blood is slightly acidic because bicarbonate is lost), from diarrhea, kidney tubule problems or some medicines 3 |
| 3. Chloride alone | Normal | Normal | Often a draw or hydration blip, or recent saline through a drip; usually repeated before anything else |
Vomiting usually does the opposite: losing stomach acid lowers chloride and raises bicarbonate. If your bicarbonate is the line that is low, the companion page on low bicarbonate covers it from that side. A broader walk through all the electrolytes is in electrolytes explained.
Read these beside your chloride
- 1Sodium high or high-normal, bicarbonate normalA repeat basic metabolic panel after a week or so of normal drinking is the usual next step. If you have been told to limit fluids, keep to that limit and ask your clinician how to retest.
- 2Bicarbonate lowAsk your clinician to work out the anion gap and check kidney function and potassium. Do not wait for a routine retest.
- 3Sodium and bicarbonate both normalAsk whether a repeat test, taken well hydrated, is needed before anything is read into it.
Work out your anion gap
The anion gap separates pattern 2 from other kinds of acidosis. It is sodium minus the sum of chloride and bicarbonate. On most modern analysers a normal gap is about 4 to 12 mEq/L, though some labs still print an older 8 to 16 range 2. A worked example: sodium 140, chloride 110, bicarbonate 20 gives 140 minus 130, an anion gap of 10. That is a normal gap, so the low bicarbonate is matched by the high chloride, which points to bicarbonate being lost rather than an acid being added.
A high anion gap points elsewhere, to an unmeasured acid such as ketones or lactic acid using up bicarbonate without chloride rising 2; the page on a high anion gap covers that side. Albumin, the main blood protein, also carries negative charge, and each 1 g/dL fall in albumin lowers the anion gap by about 2.5 2, so a low albumin can hide a raised gap.
CalculatorAnion gap calculatorPut in your sodium, chloride, bicarbonate and albumin to get a corrected anion gap.Work it out What causes high chloride
Common causes
- Dehydration and water loss. Not drinking, fever, heat, or heavy sweating without drinking. Sweat holds less salt than blood, so sweating loses more water than salt and leaves sodium and chloride concentrated.
- Diarrhea. Gut fluid below the stomach is rich in bicarbonate. Losing litres of it drops blood bicarbonate, and the kidneys hold on to chloride in its place 3.
- Normal saline through a drip. 0.9% saline contains 154 mmol/L of chloride, about 50% more than plasma, so several litres in hospital raise blood chloride 5.
- Medicines that make the kidneys lose bicarbonate. Acetazolamide (used for altitude sickness and glaucoma) and topiramate (used for migraine and seizures) can cause a normal-gap, high-chloride acidosis 3.
Less common causes
- Renal tubular acidosis (RTA), where the kidney tubules fail to reclaim bicarbonate or excrete acid. Potassium helps sort the type: low in types 1 and 2, high in type 4 3.
- Early chronic kidney disease, before the anion gap rises 3.
- Long-standing fast breathing (chronic respiratory alkalosis), from overbreathing, pregnancy or living at altitude. The kidneys lower bicarbonate to compensate and chloride rises in step 3.
- A urinary diversion that routes urine through a piece of bowel, which swaps urine chloride for blood bicarbonate 3.
- Diabetes insipidus, where the body loses large volumes of dilute urine and sodium and chloride climb together.
Does high chloride cause symptoms?
High chloride by itself rarely causes symptoms. The symptoms come from the cause. Dehydration brings thirst, dark urine, a dry mouth and dizziness on standing. Bicarbonate loss from diarrhea brings the diarrhea itself. A more marked acidosis can bring deep, fast breathing, tiredness and, in children, poor feeding.
What your doctor may check next
- A repeat basic metabolic panel once you are well hydrated.
- A venous blood gas, which measures blood pH and confirms whether there is an acidosis.
- The anion gap, corrected for albumin.
- Kidney function: creatinine, eGFR and urea (BUN). See kidney function explained.
- Potassium, which separates the types of renal tubular acidosis.
- A urine anion gap (urine sodium plus potassium minus chloride): negative in diarrhea-related acidosis, positive or near zero in distal RTA 4.
- A medication review, looking for acetazolamide, topiramate and recent IV fluids.
Kidney and potassium checks
If one of those also came back flagged, the pages on high creatinine, high BUN, high potassium and low potassium pick up from there. The eGFR calculator turns a creatinine into a filtration estimate.
How high chloride comes back down
High chloride falls when its cause is dealt with. Water loss corrects with drinking, or with fluids in hospital if you cannot keep them down. If you have been told to limit fluids for heart failure, kidney disease or low sodium, follow your clinician's limit rather than drinking more. Confusion, fainting, very little urine or being unable to keep fluids down needs same-day care, not more water at home.
Diarrhea-related bicarbonate loss settles as the diarrhea stops and the losses are replaced. If a medicine such as acetazolamide or topiramate is the cause, the prescriber decides whether to change it; never stop a prescribed medicine on your own. In hospital, the drip fluid matters too: in the SMART trial of 15,802 critically ill adults, balanced fluids with less chloride lowered the 30-day rate of death, new dialysis or lasting kidney damage from 15.4% with saline to 14.3% 5.
Almost all dietary chloride comes from salt (sodium chloride). Cutting heavily salted processed food helps chloride mostly when sodium is high too; it does little for a high chloride caused by bicarbonate loss. No supplement has evidence for lowering chloride. Exercise matters through sweat: long sessions in the heat without enough to drink can raise both sodium and chloride on a test taken soon after.
Your clinician sets the retest timing by cause: often a repeat after a week or so of normal drinking for a dehydration reading, while a pattern 2 result is followed until bicarbonate is back in range.
Trends beat one reading
A single chloride of 108 with normal sodium and bicarbonate rarely matters. A chloride that climbs over several tests while bicarbonate falls does. That divergence is the signature of ongoing bicarbonate loss 3, and it is easy to miss when each result sits just outside the flag. Compare results across tests in the same units, and from the same lab where you can; trends beat single readings explains how.
Citations
- MedlinePlus. Chloride Blood Test. US National Library of Medicine.
- Kraut JA, Madias NE. Serum anion gap: its uses and limitations in clinical medicine. Clin J Am Soc Nephrol. 2007;2(1):162-174.
- Kraut JA, Madias NE. Differential diagnosis of nongap metabolic acidosis: value of a systematic approach. Clin J Am Soc Nephrol. 2012;7(4):671-679.
- Batlle DC, Hizon M, Cohen E, Gutterman C, Gupta R. The use of the urinary anion gap in the diagnosis of hyperchloremic metabolic acidosis. N Engl J Med. 1988;318(10):594-599.
- Semler MW, Self WH, Wanderer JP, et al. Balanced crystalloids versus saline in critically ill adults (SMART). N Engl J Med. 2018;378(9):829-839.
- Berend K, van Hulsteijn LH, Gans RO. Chloride: the queen of electrolytes? Eur J Intern Med. 2012;23(3):203-211.
Educational context only, not medical advice or a diagnosis. Always discuss your results with a clinician.
