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Anion gap is a measure of the balance between acid and base in your blood. A high value can indicate that your blood is more acidic than normal. A low value can indicate that your blood is not acidic enough.[1]
On this page you can read what anion gap is, what the guidelines say about a value that is too low or too high, what affects your value and which values are best to look at alongside it.
Also known as: anion gap, serum anion gap. At the lab: n/a.
Electrolytes are minerals that take on an electrical charge when they dissolve in water or body fluids. You get them from what you eat and drink. They help regulate the balance between acid and base in your blood. Examples are sodium, chloride, potassium and bicarbonate.[1]
Some electrolytes are positively charged, others negatively. The anion gap is the difference, or the gap, between those two groups. The lab does not measure the anion gap on its own: it is a calculation using the results of other blood values.[1]
Too much acid in your blood and too little acid in your blood can both be serious. The anion gap helps show whether your blood is out of balance and whether your electrolytes are out of balance.[1]
A healthcare provider may order the test if you have symptoms such as shortness of breath, vomiting, confusion, tiredness or a very fast heartbeat. These symptoms can fit with blood that is too acidic.[1]
Blood that is not acidic enough can come with other symptoms. Think of an irregular heartbeat, irritability, shaking hands, muscle twitches, nausea and numbness or tingling in your face, hands or feet.[1]
The anion gap tells you something about the health of many functions in your body. Still, there are many normal results and many possible causes of an abnormal one. That is why you should discuss your result with your healthcare provider.[1]
| Result | What it can point to | Who it is for |
|---|---|---|
| Normal[1] | What counts as normal differs from lab to lab | Everyone who has had the test |
| Too high[1] | Blood that is more acidic than normal | Everyone who has had the test |
| Too low[1] | Blood that is not acidic enough; rare, a new test often follows | Everyone who has had the test |
Source: MedlinePlus, U.S. National Library of Medicine. The source gives no figures; normal values vary from lab to lab.[1]
A high anion gap can indicate too much acid in your blood. Possible causes include dehydration, diarrhoea, too much exercise, a kidney condition, a metabolic condition in which the body produces acids, too much aspirin or antifreeze poisoning.[1]
A low anion gap can indicate blood that is not acidic enough. A result like this is rare, so your healthcare provider will usually have you tested again. The most common cause is low albumin, a protein in your blood. That can fit with eating too little protein, kidney problems or a liver or heart condition.[1]
BioProfile is working on its own zones for each value, from risk to optimal. A doctor reviews those zones before they appear in your result.
The source lists dehydration and diarrhoea as possible causes of a high anion gap.[1]
Too much exercise can make your blood more acidic. That can give a higher anion gap.[1]
Too much aspirin can lead to poisoning that raises your anion gap. Tell your healthcare provider which medicines you take.[1]
Eating too little protein can lower your albumin. Low albumin is the most common cause of a low anion gap.[1]
Anion gap is included in BioProfile 121 and 150.[2]
The BioProfile editorial team wrote this page on 10 October 2026 from the sources below, which we read on 10 October 2026. Every number on this page appears in one of those sources, with that source's number next to it. An expert has yet to check this page; after that check, the expert's name and the date of the check will appear at the top. This page offers explanation, not a diagnosis. Discuss a value outside the range with your GP.
