This sodium deficit in hyponatremia calculator determines the Na deficit in mEq based on patient gender, weight serum and desired Na values. Discover more about hyponatremia and low Na values below the form.

Patient Gender:*
Patient normal weight:*
Serum Na:*
Desired Na:*

How does this sodium deficit in hyponatremia calculator work?

This is a useful health tool that allows you to compute the Na deficit according to the personalized patient data. In order for the sodium deficit in hyponatremia calculator to employ the below formula you need to input the:

- Patient’s gender  –  for the formula to use a variable which is 0.6 for males and 0.5 for females.

- Normal weight – is used in establishing the sodium correction and can be input in either lbs or kg.

- Serum Na – which is the current sodium level of the patient as resulted from a blood test.

- Desired Na – value that is established to be attained by the patient.

The formula used is:

Na Deficit = Gender variable * Normal Weight * (Desired Na – Serum Na)

In some cases you may also find Na Deficit = TBW * (Desired Na – Serum Na)


TBW (total body water) = Gender variable * Normal Weight

Example calculation

Let’s take the example of a female aged 35, with a weight of 125 lbs and serum Na levels of 124 mEq/L. The desired Na value for her is set at 145 mEq/L. The result returned by this calculator is: Estimated Na deficit is 595.34 mEq/L (or 0.60 eq).

Hyponatremia and sodium deficit

This is a condition best defined as a relative excess of water in relation to body sodium, it can be either acute or chronic, in the first case, the risk of developing neurological symptoms resulting in cerebral edema being higher. There are three types:

-Hypovolaemia – both sodium levels and body water are low.

-Normovolaemia – sodium levels are lower and body water is normal.

-Hypervolaemia – where body water is in excess to either Na.

Serum sodium levels in the normal range are between and mEq/L, everything that falls under 136 mEq/L is considered hyponatremia. Recognizing the right levels of sodium deficit is essential in treating moderate to severe hyponatremia with saline solutions.

Amongst causes for this increase in body water: primary polydipsia (excessive water intake), renal failure, ADH hormonal irregularities, adrenal insufficiency, hypothyroidism etc. Other risk factors include diarrhea, vomiting, use of diuretics or skin loss such as burns.

Signs and symptoms

This condition usually presents symptoms but this is not compulsory. Symptoms usually occur within an acute episode with a marked decrease of serum sodium. Levels between 120 -130 mEq/L are not considered with high risk for neurological issues but everything below 120 mEq/L is.

This begins with nausea, fatigue, headache or dizziness and a state of lethargy in mild cases. Moderate symptoms include the above and muscle cramps, behavioral changes and confusion. Severe hyponatremia may lead to impaired mental status, seizures and even coma in severe cases.

Sodium deficit diagnostic tests

The main investigations to determine the Na deficit include the serum sodium through a blood test, the serum potassium to eliminate other diagnostics, plasma and urine osmolality. There are several other tests used to exclude other conditions such as the Serum thyroid-stimulating hormone and free thyroxine level to exclude hypothyroidism, adrenocorticotropic hormone ACTG stimulation to exclude adrenal suppression.


1) Adrogué HJ, Madias NE. (2000) Hyponatremia. N Engl J Med; 25;342(21):1581-9.

2) Mohmand HK, Issa D, Ahmad Z, Cappuccio JD, Kouides RW, Sterns RH. (2007) Hypertonic saline for hyponatremia: risk of inadvertent overcorrection. Clin J Am Soc Nephrol; 2(6):1110-7.

23 May, 2015