Sodium 155 mEq/L
= 155 mmol/L in SI units
Contact your doctor promptly to discuss this result.
- Critically low (severe hyponatremia)
- Severely low
- Moderately low
- Mildly low
- Normal
- Borderline high
- Moderately high
- Severely high
- Critically high (severe hypernatremia)
At a glance
- Your band
- Severely high · 155–16 mEq/L
- Distance from typical range
- 9 mEq/L above 146
- SI units
- 155 mEq/L = 155 mmol/L
What 155 mEq/L means
A sodium of 155 mEq/L is severely high — some labs already flag values from 155 mEq/L as critical — and it needs urgent same-day medical evaluation.
At this level the blood is markedly concentrated and water is being pulled out of brain cells. Weakness, irritability, and confusion become common, and the margin before truly critical territory (160 mEq/L and above) is small. Sodium this high in an adult almost always means a substantial water deficit the body could not correct on its own — from major fluid losses, an inability to drink enough, or a kidney water-handling problem such as diabetes insipidus (arginine vasopressin disorder). Whether treatment happens in the emergency department or another same-day setting depends on symptoms and how fast the level rose, but this result must not wait.
Most US labs report a normal adult sodium range of about 135 to 145 mEq/L (the convention used by MedlinePlus and Mayo Clinic); some labs use 136 to 145. Critical (panic) cutoffs vary slightly between labs: sodium at or below 120 mEq/L is widely treated as a critical low, and 160 mEq/L and above as a critical high, though some labs flag highs starting at 155.
Common causes
- Significant dehydration from prolonged vomiting, diarrhea, or fever
- Inability to drink enough (frailty, serious illness, impaired thirst, limited access to water)
- Diabetes insipidus — the kidneys pass large volumes of dilute urine
- Uncontrolled diabetes with heavy urination (osmotic diuresis)
- Heatstroke or heavy sweating without adequate water replacement
- Diuretic use combined with poor fluid intake
- Rarely, excess salt intake such as hypertonic fluids or salt poisoning
Symptoms that can go with it
- Intense thirst (or, worryingly, little thirst despite dehydration in older adults)
- Weakness and lethargy
- Irritability or restlessness
- Confusion
- Muscle twitching
- Very dry mouth and skin
- Reduced urination (or unusually large volumes of pale urine with diabetes insipidus)
Sensible next steps
- Seek medical evaluation today — call your clinician now, and go to the emergency department if you cannot be seen today, cannot keep fluids down, or the person tested is elderly, frail, confused, or very drowsy.
- Drink water in steady amounts unless a doctor has restricted your fluids, but do not rely on self-treatment alone at this level — correction should be monitored.
- Expect repeat blood tests and urine studies to work out whether the problem is fluid loss, kidney water handling, or intake.
- Bring your medication list, especially diuretics, lithium (which can cause diabetes insipidus), and laxatives.
- Follow up until the sodium is confirmed back in range — bringing it down too fast carries its own risks, so correction is gradual and supervised.
Frequently asked questions
Is 155 mEq/L a normal sodium level?
No. 155 mEq/L is well above the normal 135–145 mEq/L range — severe hypernatremia — and needs urgent same-day medical attention.
Is a sodium level of 155 dangerous?
Yes, potentially. At 155 mEq/L water is being drawn out of brain cells, and weakness and confusion become common. Treat this as an urgent same-day medical issue, and go to the ER if there is confusion, extreme drowsiness, or an inability to keep fluids down.
What causes low blood sodium (hyponatremia)?
Low sodium almost always means too much water relative to sodium, not too little salt in the diet. Common causes include thiazide diuretics (water pills), antidepressants such as SSRIs, drinking large amounts of water, vomiting or diarrhea, SIADH (excess antidiuretic hormone from lung, brain, or medication causes), and heart, liver, kidney, thyroid, or adrenal conditions. Very high blood glucose can also dilute the measured sodium. Your clinician uses urine tests and your fluid status to sort out which applies to you.
Can drinking too much water cause low sodium?
Yes. Drinking water faster than your kidneys can excrete it dilutes your blood sodium — this is water intoxication. It is a known risk during endurance events when people drink heavily without eating, in people who drink very large volumes habitually, and when illness or medications limit how much water the kidneys can release. For most healthy people, drinking to thirst is the safest guide; there is no need to force extreme volumes of water.
Does eating too much salt raise my blood sodium level?
Usually not. A salty diet makes you thirsty and makes your body hold water, which raises blood pressure and causes puffiness — but the blood sodium concentration typically stays normal because thirst and the kidneys rebalance it. High blood sodium (hypernatremia) is almost always a shortage of water rather than an excess of dietary salt. That said, a lower-salt diet is still worthwhile for blood pressure and heart health, which is a separate issue from this test result.
Should I go to the ER for a sodium of 155 mEq/L?
Quite possibly. 155 mEq/L needs same-day evaluation — call your clinician now, and go to the ER if you cannot be seen today, cannot keep fluids down, or the person tested is elderly, frail, confused, or very drowsy.
Why is my sodium low if I eat plenty of salt?
Because blood sodium is a concentration, not a measure of salt intake. Low sodium nearly always means your body is holding on to extra water that dilutes the sodium — from medications, hormones like ADH, drinking large volumes, or conditions such as heart, liver, or kidney disease. Adding more salt to your food rarely fixes it and can be harmful in some of these conditions, so the right move is finding the cause with your clinician rather than changing your diet on your own.
Check a different Sodium value
Sources
- Sodium Blood Test — MedlinePlus (National Library of Medicine)
- Electrolyte Panel — MedlinePlus (National Library of Medicine)
- Hyponatremia — Symptoms and Causes — Mayo Clinic
- Hyponatremia (StatPearls) — NCBI Bookshelf / StatPearls
- Hypernatremia (StatPearls) — NCBI Bookshelf / StatPearls
Educational information, not medical advice. Reference ranges vary between labs — always compare with the range printed on your own report and discuss results with your doctor. Full disclaimer