Blood Ionogram: Definition

The blood ionogram is one of doctors’ most commonly ordered tests to monitor the body’s water and electrolytic balance.

What is a blood ionogram?

The blood ionogram is an extremely common test – and one of the most requested, which corresponds to the determination of the principal ionic constituents of the blood (or electrolytes). Namely sodium (Na), potassium (K), calcium (Ca), chlorine (Cl), magnesium (Mg), and bicarbonates (CO3).

The blood ionogram is routinely prescribed as part of a check-up. It is also requested to help with diagnosis when a patient has symptoms such as edema (i.e. fluid accumulation), weakness, nausea and vomiting, confusion, or irregular heartbeat.

The examination is used to monitor the hydro electrolytic balance of the body, i.e. the balance between water and different ions. It is mainly the kidneys that ensure this balance, filtering urine, but the skin, breathing, and digestive system also take care of it.

Often, the doctor asks for a urinary ionogram at the same time, to be able to play the part of the kidneys in any metabolic disorders presented on the blood ionogram.

Note that the level of phosphorus, ammonium, and iron can also be determined during a blood ionogram.

Normal values of the blood ionogram

Here are the so-called normal values of the main ionic constituents of blood:

  • Sodium (natremia): 135 – 145 mmol/l (millimoles per litre)
  • Potassium (kalemia): 3.5 – 4.5 mmol/l
  • Calcium (serum calcium): 2.2 – 2.6 mmol/l
  • Chlorine (chloremia): 95 – 105 mmol/l
  • Magnesium: 0.7 – 1 mmol/l
  • Bicarbonates: 23 – 27 mmol/l

Note that these values may vary depending on the laboratories performing the analyses. In addition, they vary slightly depending on age.

How to prepare and conduct the exam

Before going to the exam, there are no special conditions to be met. For example, it is not necessary to be fasting.

The examination consists of a venous blood test, usually in the crease of the elbow. The blood thus collected is then analyzed.

Analysis of the results


An increase in sodium levels in the blood – called hypernatremia – may be linked to:

  • dehydration by digestive loss;
  • decreased fluid intake
  • heavy sweating;
  • sodium overload.

On the contrary, a decrease in blood sodium levels – we speak of hyponatremia – is to be associated with:

  • a deficit in sodium intake with digestive or renal losses;
  • or an increase in the amount of water.

Hyponatremia can be a sign of heart failure, kidney or liver failure, or edema.


An increase in potassium levels or hypokalemia occurs during potassium supplementation or because of taking certain medications (anti-inflammatory, antihypertensive, etc.).

On the contrary, a drop in blood potassium levels or hypokalemia can occur in case of vomiting, diarrhea, or taking diuretics.


An increase in blood chlorine concentration or hyperchloremia may be due to:

  • severe dehydration due to sweating;
  • digestive losses;
  • sodium overload.

A decrease in blood chlorine or hypochloremia may be due to:

  • profuse, repeated vomiting
  • breathing problems
  • an increase in the amount of water (heart, kidney, or liver failure)
  • decreased sodium intake.


Hypercalcemia (high levels of calcium in the blood) may be a sign of:

  • osteoporosis;
  • hyperparathyroidism
  • vitamin D poisoning
  • prolonged immobilization (being lying down for too long);
  • or Paget’s disease, in which bones grow too quickly.

On the contrary, hypocalcemia (low blood calcium levels) can be explained by:

  • malnutrition;
  • alcoholism;
  • bone decalcification
  • chronic renal failure
  • or a defect in the absorption of the intestine.


An increase in magnesium levels may be observed:

  • in case of renal insufficiency;
  • or following the taking of magnesium-based supplements.

On the contrary, a decrease in blood magnesium concentration can be a sign of:

  • poor diet (especially among athletes);
  • excessive alcohol consumption;
  • digestive problems, etc.


High levels of blood bicarbonates may be a sign of:

  • respiratory failure
  • repeated vomiting or diarrhea

Low levels of bicarbonates in the blood can mean:

  • metabolic acidosis
  • kidney failure
  • or liver failure.

Image Credit: Photo by National Cancer Institute on Unsplash

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