Sodium · low result
What does a low Sodium mean?
Short answer
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.
Medically reviewed by Youmna DiStefano, MD · Last reviewed September 2026
When does this result need same-day care?
- Sodium below about 125 mmol/L, or any low value with confusion, vomiting or seizures — emergency care
What is the normal range for Sodium?
- age 18+: 135 – 145 mmol/L
Can reflect overhydration, certain medications (especially diuretics), or hormonal conditions.
Full reference table, citations and testing options: Sodium biomarker page.
What are the common causes of low Sodium?
- Thiazide diuretics, SSRIs, carbamazepine, antipsychotics, NSAIDs
- Excess water intake relative to salt (endurance events, beer potomania, some diets)
- Heart failure, cirrhosis, kidney disease
- SIADH from illness, pain, surgery, or lung/brain disorders
- Hypothyroidism, adrenal insufficiency
- Vomiting, diarrhea with water replacement only
What symptoms go with low Sodium?
- Often none when mild and chronic
- Nausea, headache, fatigue
- Confusion, unsteadiness, falls
- Seizures when severe or rapid
What do 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 available at TestWell: TSH (Thyroid Stimulating Hormone) ($26.99), TSH + Free T4 ($27.99), Cortisol (AM) ($26.99), Cortisol ($32.99).
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 | $20.99 | Yes | 1–3 business days |
Common questions
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.
Sources
Educational content, not a diagnosis. Lab results are one input; a clinician interprets them with your history and exam.