Sodium 118 mEq/L: Is That Low?

Is Sodium 118 mEq/L Low, Normal, or High?

Sodium 118 mEq/L is severely low and falls well below the normal range of 135 to 145 mEq/L. At 118 you are 17 points under the bottom of the normal band and 7 points below the 125 mark that most doctors treat as a red flag for severe hyponatremia. A number this low is rarely about salt alone. In most cases it points to a problem with how the body is handling water rather than a shortage of salt in the diet. The reassuring part is that almost every common cause behind this result has a clear name and a clear path forward, which is exactly what this page walks through.

Hidden Risk of Sodium 118 mEq/L

The biggest danger at 118 is what low sodium does to the brain. When blood sodium drops, water moves into brain cells and they swell. Inside the hard shell of the skull there is no room to expand, so pressure builds and can cause confusion, severe headache, vomiting, seizures, or loss of consciousness. Speed matters more than the exact number, but 118 is low enough that symptoms are common, especially if the drop happened quickly.

• Brain swelling is the main acute threat at this level
• Falls and injury from dizziness or sudden confusion
• Seizures, which can appear with little warning
• Correcting sodium too quickly can itself harm the brain, so this must be done by a clinician

What Does a Sodium Level of 118 mEq/L Mean?

Think of your blood as a glass of saltwater. Sodium is the salt and the level is really a measure of salt versus water. A reading of 118 usually does not mean you lost a huge amount of salt. It much more often means your body is holding on to too much water, which waters down the salt that is there. So the question doctors ask is not only how much sodium you have, but why the water is not leaving. The most common reason is a hormone called ADH, short for antidiuretic hormone, that tells the kidneys to keep water. When ADH is too active, water builds up and the sodium concentration falls. This is why two people can eat the same amount of salt yet have very different sodium levels. A wide range of triggers can switch ADH on, from certain medicines to lung and brain conditions, which is why the cause has to be tracked down rather than guessed. Heart failure, liver disease, and kidney disease can also drive a number this low by changing how the body senses and stores fluid, so the kidneys hold water even when the blood is already too dilute. Understanding this also explains why simply eating more salt rarely fixes a number this low on its own, and why the fix is matched to the cause rather than applied the same way for everyone.

Lifestyle Changes for Sodium 118 mEq/L

At a true 118, lifestyle tweaks are not the fix. This is a level that is evaluated and managed in a medical setting, often the same day. Still, there are habits that help your care team find the cause faster. Keep a simple log of how much fluid you drink each day, including water, tea, coffee, and sports drinks, because heavy water intake is a frequent trigger and a hidden one. Note any new dizziness, nausea, or mental fog and when it started, since the timing helps separate a sudden drop from a slow one. Avoid driving if you feel foggy or unsteady, and ask someone to come with you to any appointment. Bring a list of every medicine and supplement you take, since many of the most common causes are tied to drugs. Do not try to load up on extra water to feel better, because that can push the number even lower and make the situation more dangerous. It also helps to note your recent weight if you know it, since a gain over days can signal water buildup, and to mention any recent illness, surgery, or new medicine. These small details often point straight at the most common causes and can save hours in the search for an answer.

Diet Changes for Sodium 118 mEq/L

Diet is a smaller piece of the puzzle at 118 than most people expect, and large amounts of plain water can make a true low worse rather than better. Once your doctor identifies the cause, they may set a daily fluid limit, which is the most common dietary step for water-driven hyponatremia. Salt tablets or salty foods are used only when a clinician decides the cause calls for it, never as a guess at home.

• Follow any fluid restriction your care team sets, often around 1 to 1.5 liters per day
• Spread fluids through the day instead of drinking a lot at once
• Limit beer and other low-salt, high-volume drinks that dilute sodium
• Do not add salt aggressively on your own, since the cause may not be salt loss

Sodium 118 mEq/L in Men, Women, Elderly, and Kids

A 118 reading is read against the same normal range for everyone, but the likely cause shifts with age and situation. Older adults are the most common group to land here, partly because of water pills, certain antidepressants, and a thirst system that changes with age. They may also show only subtle signs, like a fall or new confusion, rather than dramatic symptoms. Younger women after surgery can be more sensitive to low sodium, which is why post-operative readings are watched closely and corrected carefully. In endurance athletes, drinking too much water during long events can drop sodium sharply within hours, a pattern sometimes seen after marathons. In small children, illness with vomiting and the wrong rehydration fluids can be a cause, and their smaller bodies shift sodium quickly. The National Kidney Foundation notes that the underlying driver, not age alone, guides treatment, so the same number can mean different things in different people. Knowing which group you fall into helps your doctor rank the likely causes from most to least probable and choose the first tests accordingly.

Medicine Effects on Sodium 118 mEq/L

Medicines are among the most common reasons a sodium level reaches 118, so your full drug list is one of the first things a clinician reviews. Many of these drugs are very common, which is why this result shows up often in everyday practice. Never stop a prescribed medicine on your own based on a lab number, because some need careful tapering and abrupt changes carry their own risks.

• Thiazide water pills are a leading drug cause of low sodium
• Some antidepressants, especially SSRIs, can lower sodium
• Carbamazepine and certain seizure or pain drugs are linked to it
• Desmopressin and some chemotherapy agents can also play a role

When to Retest Sodium 118 mEq/L

A true 118 is not a number to recheck casually at a later date. It is usually confirmed quickly and managed right away, often with repeat blood draws every few hours while sodium is brought up slowly and safely. The deliberate pace is on purpose, because raising sodium too fast can injure the protective coating around nerves, a serious complication doctors work hard to avoid. After the cause is treated, your doctor will set a follow-up schedule, which may mean weekly checks for a while and then less often once the level is stable. Each recheck also shows whether the treatment is working or needs adjusting. If a sample looks oddly low and you have no symptoms at all, a careful clinician may repeat it promptly to rule out a lab error before acting, but they will not simply ignore a confirmed value this far below normal.

Sodium 118 mEq/L — Frequently Asked Questions

When to See a Doctor About Sodium 118 mEq/L

A sodium of 118 calls for medical care now, not later. If you have confusion, a severe headache, repeated vomiting, drowsiness that is hard to shake, a seizure, or any trouble waking someone, treat it as an emergency and seek urgent care immediately. Even without dramatic symptoms, a confirmed level this low should be evaluated the same day, because the safest correction is slow and supervised, and waiting can allow the brain to come under more strain. Bring your medicine and supplement list, since the most common causes are tied to drugs and fluids, and mention how much water you have been drinking. Do not drive yourself if you feel unwell, and let someone know where you are going. This page is educational and not a substitute for the judgment of your own clinician, who can match the number to your full history and symptoms and decide how quickly and how slowly to correct it.

Written by

Ernestas K.

Clinical research writer specializing in human health, biology, and preventive medicine.

Reviewed against NIH, AHA, Mayo Clinic, NKF guidelines · Last reviewed June 11, 2026