Updated December 29, 2014.

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Working as a kidney doctor, I see and treat patients both in and out of the hospital. One of the most common electrolyte and mineral complications that I see, especially in a hospital setting, is hyponatremia, or a low sodium level. Many times the sodium level can be dangerously low. This is a more common occurrence in adults and elderly who severe sodium restrict but also may be on certain medications like diuretics that can not only cause hyponatremia but also exponentially worsen this problem if the person is severely salt restricting at home.

To try and put this in some perspective,  a "sodium level" is something that can be measured on routine lab work. A "normal level" is usually in the range of 135-140 and the units are measured in milliequivalents per liter (or meq/L for short). Many times I see people in the 120s range, even in the low 120s range. Too low a level as well as a very low sodium level can have devastating neurologic consequences. Low sodium levels can affect your thinking and cognition. Very low sodium levels or an acute change in levels over a short period of time has the potential to cause brain changes.

Common symptoms of low sodium can be increasing weakness, fatigue, confusion, nausea, vomiting, headache, muscle pain or twitching; basically any or all of the above. 

In whom do I see this most commonly occurring?

This most commonly occurs in elderly people, especially those on diuretics. This can happen in many adults especially if they are on diuretics because they are used in the treatment of high blood pressure.

In my experience, if an elderly individual is told to "sodium restrict" they will not take in any sodium. They will find ways to completely eliminate any form of sodium from their diet. They are so deathly afraid of going into acute Congestive Heart Failure (CHF), that they won't take any salt in and they will continue to take their diuretics. The same principle can occur if they get, say a 24 hour flu bug and transient viral gastroenteritis or diarrhea. They can become dehydrated yet often will be taking their diuretic often for fear of developing CHF and not being able to breathe. 

Do Not Severely Sodium Restrict

If you are in the hospital and the doctors put you on a sodium restriction, understand that you will be at least be on a 1500-2000 mg a day. Even those who are in the advanced stages of CHF are placed on a sodium restriction no lower than 1500 mg daily. Your body needs sodium to function, the cells in your body need a certain amount of sodium to function. A certain amount of sodium each day is needed to maintain the right concentration in the blood stream so that the brain doesn't get affected.

How to Prevent This From Happening

If you were told by your doctor to sodium restrict, ask him/her to quantify the amount and explain it so that it makes sense to you. Do not go below 2000 mg a day unless there is a good reason to such as advanced CHF as mentioned above.   

If you are the son or daughter of an elderly parent, and they are on  a diuretic please have their doctor tell them not to completely eliminate sodium from their diet. They won't listen to you, they need to hear it first hand from their doctor.

If you are placed on  a diuretic for the treatment of high blood pressure, such as hydrochlorothiazide or chlorthalidone, you should be receiving bloodwork to assess your sodium level, in addition to your potassium level and kidney function. If the dose is increased, you may need to have blood work a week or so later in order to see if there have been any changes in your sodium level.

If you develop nausea, vomiting, or diarrhea, talk with your doctor to see if s/he wants you to hold the water pills while you are dealing with the acute illness.  Note that there are many causes of hyponatremia; that discussion is for another blog post.