--- title: Sodium Test type: biomarker url: "https://www.test-well.com/biomarkers/sodium" also_known_as: - sodium - na category: Metabolic Health units: - mmol/L - mEq/L order_price_usd: 20.99 order_item: Basic Metabolic Panel order_url: "https://www.test-well.com/tests/basic-metabolic-panel" reviewed_at: 2026-09-06 --- # Sodium > Sodium is measured with a standard blood draw after an 8–12 hour fast. A typical reference range is 135 – 145 mmol/L. At TestWell it's $20.99 all-in as Basic Metabolic Panel, results in 1–3 business days, drawn at Quest or Labcorp. An out-of-range result is a prompt to look closer, not a diagnosis. Also known as: sodium, na. ## Key facts | Fact | Value | | --- | --- | | Units | mmol/L / mEq/L | | Sample | Blood draw | | Fasting | 8–12 hours | | Results | 1–3 business days | | Price | $20.99 | | Labs | Quest or Labcorp · BioReference in NY/NJ | ## What does Sodium measure? A key electrolyte that controls fluid balance, blood pressure, and nerve and muscle function. ## What is the normal range for Sodium? | Population | Reference range | | --- | --- | | age 18+ | 135 – 145 mmol/L | Reference intervals differ slightly between labs; the range printed on your report is the one to interpret against. Ranges are usually set so 95% of healthy people fall inside them. ## What does a high Sodium mean? High sodium (hypernatremia) almost always means water loss exceeding intake — not eating too much salt. Dehydration from illness, heavy sweating, diuretics, uncontrolled diabetes, or an impaired sense of thirst (older adults, certain brain conditions) are typical causes; diabetes insipidus is rare. Mild elevations correct with fluids; significant ones need medical evaluation. ### Common causes of high Sodium 1. Dehydration: inadequate water intake, fever, heat, vomiting, diarrhea 2. Osmotic diuresis from very high glucose 3. Diuretics, lithium (impairs water retention) 4. Impaired thirst in older adults or neurological disease 5. Diabetes insipidus (rare) ### Symptoms that go with high Sodium - Thirst, dry mouth - Confusion, lethargy, irritability when marked ### What clinicians usually check next - Repeat after rehydrating - Glucose, kidney function - Urine osmolality if persistent Follow-up tests at TestWell: [Glucose](https://www.test-well.com/tests/glucose-basic) ($14.99). ### Seek care promptly if - Sodium above about 150 mmol/L, or any elevation with confusion — same-day care **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 does a low Sodium mean? Low sodium (hyponatremia) is the most common electrolyte abnormality and has many causes: thiazide diuretics, SSRIs and other medications, excess water intake, heart, liver or kidney disease, hypothyroidism, adrenal insufficiency and SIADH (inappropriate antidiuretic hormone from illness, pain, medications or lung and brain conditions). Mild, chronic low sodium is common in older adults; rapid or severe drops cause confusion and seizures. ### Common causes of low Sodium 1. Thiazide diuretics, SSRIs, carbamazepine, antipsychotics, NSAIDs 2. Excess water intake relative to salt (endurance events, beer potomania, some diets) 3. Heart failure, cirrhosis, kidney disease 4. SIADH from illness, pain, surgery, or lung/brain disorders 5. Hypothyroidism, adrenal insufficiency 6. Vomiting, diarrhea with water replacement only ### Symptoms that go with low Sodium - Often none when mild and chronic - Nausea, headache, fatigue - Confusion, unsteadiness, falls - Seizures when severe or rapid ### What clinicians usually check next - Repeat to confirm; review medications and fluid habits - TSH and morning cortisol - Urine sodium and osmolality to classify the cause - Assessment of heart, liver and kidney function Follow-up tests at TestWell: [TSH (Thyroid Stimulating Hormone)](https://www.test-well.com/tests/tsh) ($26.99), [TSH + Free T4](https://www.test-well.com/tests/tsh-with-free-t4) ($27.99), [Cortisol (AM)](https://www.test-well.com/tests/cortisol-am) ($26.99), [Cortisol](https://www.test-well.com/tests/cortisol-labcorp) ($32.99). ### Seek care promptly if - Sodium below about 125 mmol/L, or any low value with confusion, vomiting or seizures — emergency care **Can drinking too much water lower sodium?** Yes, especially during endurance exercise or with very high fluid intake and low salt. Most hyponatremia, though, is medication- or illness-related. ## How do you get tested for Sodium? | Order | Type | Price | Includes | | --- | --- | --- | --- | | [Basic Metabolic Panel](https://www.test-well.com/tests/basic-metabolic-panel) | Single test | $20.99 | This marker | ## Quest vs Labcorp vs BioReference | Lab | Available | Price | Notes | | --- | --- | --- | --- | | Quest Diagnostics | Yes | $20.99 | Choose Quest at checkout; walk-in patient service centers in every state TestWell serves outside NY and NJ. | | Labcorp | Yes | $21.99 | Choose Labcorp at checkout; walk-in patient service centers in every state TestWell serves outside NY and NJ. | | BioReference (NY & NJ) | Yes | $22.99 | New York and New Jersey orders route here automatically — state rules keep Quest and Labcorp from accepting self-ordered draws. | ## Common questions about Sodium ### Do I need a doctor's order to test my sodium? No. TestWell's licensed physician network reviews and approves your order — usually within minutes. You can place an order online without an in-person visit or a referral from your own doctor. ### How long does it take to get Sodium results? Most Sodium results are available in 1–3 business days after your specimen arrives at the lab. You'll get an email the moment your results are ready, with everything viewable in your TestWell portal. ### How much does a Sodium test cost? Our Basic Metabolic Panel starts at $20.99. That's the all-in price — no copays, no insurance hoops, no surprise bills. HSA and FSA cards are accepted. ### Do I need to fast before my Sodium test? Yes — for the most accurate result, fast for 8–12 hours before your blood draw. Water is fine; coffee, food, and supplements are not. Your prep instructions will be included with your order. ### Which lab will process my Sodium test? Your test will be processed by Quest Diagnostics, Labcorp, or BioReference depending on which is closest to you and which lab carries the test. All three are CLIA-certified and trusted by hospitals nationwide. You'll choose your lab during checkout from 4,000+ locations. ## Sources - [Mayo Clinic Labs](https://www.mayocliniclabs.com/test-catalog/overview/8533) - [MedlinePlus (NIH) — Sodium Blood Test](https://medlineplus.gov/lab-tests/sodium-blood-test/) ## Related biomarkers - [Glucose](https://www.test-well.com/biomarkers/glucose) - [Creatinine](https://www.test-well.com/biomarkers/creatinine) - [eGFR](https://www.test-well.com/biomarkers/egfr) - [BUN](https://www.test-well.com/biomarkers/bun) - [ALT](https://www.test-well.com/biomarkers/alt) - [AST](https://www.test-well.com/biomarkers/ast) - [Reference range lookup tool](https://www.test-well.com/tools/reference-range-lookup) - [Lab unit converter](https://www.test-well.com/tools/lab-unit-converter) - [All biomarkers](https://www.test-well.com/biomarkers) --- Medically reviewed by Youmna DiStefano, MD (Medical Reviewer, TestWell); last reviewed 2026-09-06. Review policy: https://www.test-well.com/reviewers/youmna-distefano-md Canonical page: https://www.test-well.com/biomarkers/sodium Machine-readable catalog: https://www.test-well.com/api/catalog.json · MCP server: https://www.test-well.com/mcp · Overview for agents: https://www.test-well.com/llms.txt Prices are cash-pay, in USD, and include physician authorization; every order adds one flat $6 lab processing fee. Educational content is not a diagnosis — discuss results with a clinician.