
Low sodium (hyponatraemia)
Sodium is an important electrolyte that helps keep the right amount of water in and around your cells. It's also needed for your nerve and muscle function.
Low sodium (hyponatraemia) is when the concentration of sodium in your blood is below the normal range (135-145 mEq/L).
Low sodium can cause swelling within your cells leading to problems that can range from mild to serious and even life threatening.
You have an increased risk of getting low sodium as you get older, especially if you have a heart or kidney condition and take certain types of medications.
Causes of low sodium
Reasons why your sodium level might get too low include:
- Taking some medications, including water pills (diuretics), some antidepressants, pain medications and epilepsy medication.
- Having heart failure, kidney disease or liver disease, which can affect the amount of fluid in your body and your sodium level.
- Having bouts of long lasting, severe diarrhoea or vomiting in which you lose fluids and sodium.
- Drinking too much water, which can dilute the amount of sodium in your blood. This can be a problem during endurance events like marathons or triathlons when you also lose sodium through sweat.
- Having a hormone imbalance that affects your sodium level. This can happen with Addison's disease and underactive thyroid (hypothyroidism).
- Taking ecstasy (MDMA). This has been linked to serious cases of low sodium.
Symptoms of low sodium
You may not have any symptoms if your low sodium is mild. You're more likely to have symptoms if your sodium drops quickly or is very low.
Signs of low sodium may include:
- nausea or vomiting
- weakness, tiredness and lack of energy
- headache
- cramps or spasms in your muscles
- irritability and restlessness
- sleepiness
- confusion
- loss of consciousness or coma
- seizures.
Diagnosing low sodium
Because the symptoms of low sodium can vary so much from person to person, a blood test is needed to make the diagnosis. You may also need a urine test.
A routine blood test that you have for other reasons may also show low sodium.
Treating low sodium
Your treatment will depend on how severe your low sodium is and what the likely cause is.
You may be asked to cut back on how much you drink.
Other treatments aim to correct the underlying problem and may include stopping any medication that can lower your sodium.
If your sodium level is very low, you may need treatment in hospital to boost your sodium level with careful monitoring.
Preventing low sodium
There are several ways you may be able to prevent low sodium:
- Know the symptoms of low sodium. Watch for them if you have a condition that can put you at risk or take medications that can cause it, such as diuretics.
- Pay attention to how much water you're drinking, especially if you take part in high-intensity physical activities. There are two reliable ways to know how much water you should have, your thirst and the colour of your urine. You're probably getting enough water if you do not feel thirsty and your urine is pale-yellow.
- Consider taking electrolyte sports drinks if you're doing intense physical activity.
HealthInfo recommends the following pages
Written by HealthInfo clinical advisers. Page created September 2022.
Sources
The information in this section comes from the following sources, some of which may be clinically complex or not available to the general public
Canterbury Community HealthPathways – Hyponatraemia. Retrieved August 2022.
Mayo Clinic – Hyponatremia. Retrieved August 2022.
Medsafe – The Ionic Truth about Hyponatraemia. Retrieved August 2022.
WebMD – Hyponatremia. Retrieved August 2022.
Image and embedded video sources
Exhausted athlete image from Shutterstock (image ID 1081462757). September 2022.
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