Sodium · high result
High sodium (hypernatremia): what it means, causes and when it is urgent
Short answer
High sodium (hypernatremia) — above about 145 mmol/L — almost always means the body has lost more water than it has taken in, not that you ate too much salt: fever, vomiting, diarrhea, heavy sweating, diuretics, the osmotic water loss of uncontrolled diabetes, or simply not drinking enough, especially in older adults whose thirst sense is blunted and in anyone who cannot reach fluids. Diabetes insipidus — the kidneys unable to hold water because of a vasopressin problem — is the uncommon cause and produces large volumes of dilute urine. A value of 146–148 in someone who was fasting or mildly unwell is usually repeated after rehydrating; above about 150, or any high value with confusion, is urgent, and correction has to be gradual.
Medically reviewed by Youmna DiStefano, MD · Last reviewed November 2026
When does this result need same-day care?
- Sodium above about 150 mmol/L, or any elevation with confusion, extreme drowsiness, twitching or a seizure — same-day or emergency care
- A high sodium in an infant, a frail older adult, or anyone who cannot drink — same-day care; they cannot correct it themselves
- Passing very large volumes of urine with relentless thirst — prompt evaluation for diabetes insipidus
What is the normal range for Sodium?
- age 18+: 135 – 145 mmol/L
Often reflects dehydration or excess salt intake.
Full reference table, citations and testing options: Sodium biomarker page.
What are the common causes of high Sodium?
- Dehydration — fever, heat, vomiting, diarrhea, heavy sweating, or simply drinking too little; the single most common cause
- Impaired thirst or access to water — older adults, dementia, stroke, infants, anyone bed-bound or acutely ill
- Osmotic diuresis — very high blood glucose in uncontrolled diabetes pulls water out through the kidneys; also mannitol and high-protein tube feeds
- Diuretics (loop diuretics in particular) and lithium, which blunts the kidney's response to vasopressin
- Central diabetes insipidus — too little vasopressin from the pituitary after head injury, surgery, tumors or inflammation; nephrogenic diabetes insipidus — kidneys that cannot respond to it (lithium, high calcium, low potassium, inherited)
- Excess sodium intake in specific situations — hypertonic saline, sodium bicarbonate, salt-water ingestion, salt tablets without water; rare outside hospital
- Primary hyperaldosteronism and Cushing's syndrome — usually only mildly high, with low potassium and high blood pressure
- A slightly concentrated sample after prolonged fasting or a long tourniquet time — small rises only
What symptoms go with high Sodium?
- Thirst and a dry mouth — the body's own alarm, which is why hypernatremia mostly occurs when thirst is blunted or water is out of reach
- Weakness, lethargy, irritability, restlessness
- Confusion, muscle twitching, seizures and coma as the level rises or when it rises quickly
- Large volumes of pale urine and night-time urination when diabetes insipidus is the cause
What do clinicians usually check next?
- Repeat after rehydrating with water over several hours — a modest rise from a dry morning resolves
- Glucose, kidney function (creatinine, eGFR) and the rest of the metabolic panel; calcium and potassium, which affect how the kidneys handle water
- Review diuretics, lithium and any recent illness with fluid loss
- If it persists: paired serum and urine osmolality and urine sodium — dilute urine with a high serum sodium points to diabetes insipidus
- A water-deprivation test or copeptin level, and pituitary imaging, when diabetes insipidus is suspected — specialist territory
- For older adults living alone or in care: a review of fluid access and a plan for illness days
- Correction is deliberately slow (no more than about 10–12 mmol/L per day) — rapid lowering can swell the brain; this is a clinician's job once the level is high
Follow-up tests available at TestWell: Calcium Test ($16.99), Glucose Test ($14.99).
How do you recheck Sodium?
Prices are cash-pay; every order adds one $6 lab processing fee. Physician authorization is included; no insurance or referral needed.
| Test or panel | Type | Price | Fasting | Results |
|---|---|---|---|---|
| Basic Metabolic Panel | Test · 8 biomarkers | $17.99 | Yes | 1–3 business days |
Common questions
Does a salty diet raise blood sodium?
Not in a healthy person — the kidneys and thirst keep it tightly regulated. High sodium on a lab test is a water problem, not a salt problem.
What is a high sodium level?
Above the lab's upper limit, usually 145 mmol/L. 146–150 is mild and most often dehydration; above 150 is moderate and needs same-day attention; above 160 is severe. Speed matters as much as the number — a fast rise is more dangerous than a slow one.
What causes high sodium?
Losing water without replacing it: fever, vomiting, diarrhea, sweating, diuretics, high blood sugar, or simply not drinking — especially in older adults with blunted thirst. Diabetes insipidus, where the kidneys cannot hold water, is the uncommon cause and comes with huge volumes of dilute urine.
Is a sodium of 146 something to worry about?
Rarely on its own. It is one point over most ranges and is commonly a morning without fluids, a hot day or a mild illness. Drink normally and repeat; a value that stays up, or that comes with excessive thirst and urination, is the one to investigate.
How do you lower high sodium?
By replacing the water deficit — orally when possible, intravenously when not — slowly, and by treating the cause (stopping the fluid loss, correcting glucose, adjusting a diuretic, treating diabetes insipidus with desmopressin). Lowering it too fast can cause brain swelling, so significant hypernatremia is corrected under medical supervision.
What is the difference between high sodium and high blood pressure from salt?
Different things. Dietary salt can raise blood pressure over time while blood sodium stays normal, because the body retains water to match the salt. A high blood sodium means too little water relative to salt in the body — a hydration problem — and is not diagnosed by, or treated with, changes to table salt.
Educational content, not a diagnosis. Lab results are one input; a clinician interprets them with your history and exam.