Symptoms of High Sodium: Causes, Ranges, and What to Do
High sodium (hypernatremia) usually means dehydration or water loss; normal is ~135–145 mmol/L. Retest and compare at Quest—no referral needed.
A high sodium result in your blood usually means you have lost more water than salt, so the sodium in your bloodstream is more concentrated. The most common reasons are dehydration, not drinking enough fluids, or extra water loss from vomiting, diarrhea, heavy sweating, or certain medicines. One number rarely tells the whole story, so your symptoms, your kidney function, and nearby electrolytes (like potassium and chloride) matter. Sodium is one of your body’s main electrolytes. It helps control fluid balance, blood pressure, and how nerves and muscles work. Your kidneys and hormones (especially ADH/vasopressin and aldosterone) constantly adjust how much water and sodium you keep or lose. In this article, you’ll learn what high sodium (hypernatremia) can feel like, what typically causes it, and what to do next—including how to use PocketMD to make sense of your full electrolyte pattern and when a retest through VitalsVault can help you confirm whether this was a one-off or a trend.
Why Is Your Sodium High?
Not enough water intake
If you are not drinking enough fluids, your body has less water to dilute sodium in your bloodstream. This is especially common in older adults (reduced thirst), people who are sick, or anyone who cannot easily access fluids. A mild elevation can normalize quickly once you rehydrate, but it is still worth checking what else was happening around the test day.
Water loss from vomiting or diarrhea
Stomach bugs and other GI issues can cause you to lose a lot of water. Even if you also lose some sodium, the water loss often “wins,” which concentrates sodium in the blood. If your high sodium came with lightheadedness, dry mouth, or reduced urination, dehydration is a strong possibility and a repeat test after recovery can be very informative.
Heavy sweating or endurance exercise
Long workouts, heat exposure, and heavy sweating can shift your fluid balance. If you replace losses with too little fluid—or with very salty fluids without enough water—your sodium can rise. This pattern is more likely when you finish exercise dehydrated (weight down, dark urine) and can show up alongside a higher albumin or total protein from hemoconcentration.
Diuretics and other medications
Some medicines change how your kidneys handle water and electrolytes. Loop diuretics and osmotic diuretics can increase water loss; lithium can interfere with the kidney’s response to ADH and lead to excessive urination; and some laxatives can cause ongoing fluid loss. If you have heart failure and take diuretics, your sodium result needs to be interpreted alongside your symptoms, weight changes, blood pressure, and kidney labs rather than in isolation.
High blood sugar causing osmotic diuresis
When blood glucose is very high, your kidneys pull extra water into the urine to help get rid of the excess sugar. That water loss can push sodium up, even if you are drinking. In this situation, correcting glucose and rehydrating usually improves sodium, but it is important to look at the full metabolic picture (glucose, kidney function, and acid-base status).
Kidney or hormone signaling problems
Less commonly, high sodium reflects a problem with how your body senses thirst or conserves water. Conditions like diabetes insipidus (a problem with ADH signaling) can cause large volumes of dilute urine and rising sodium if water intake cannot keep up. Persistent or significant hypernatremia is a reason to involve a clinician because the cause may not be simple dehydration.
Normal level of sodium (blood)
Reference intervals differ by laboratory, assay, age, and sex — use your report's own columns as primary.
| Measure | Typical range (adult, general) | Notes |
|---|---|---|
| Sodium (Na+), serum/plasma | 135–145 mmol/L (standard) | VitalsVault optimal (typical target): 138–142 mmol/L; ranges can vary slightly by lab and hydration status. |
What You Might Notice When Sodium Is High
Intense thirst and dry mouth
Thirst is your brain’s main alarm for rising sodium concentration. If your sodium is only mildly high, thirst may be the only symptom you notice. If you do not feel thirsty despite a high sodium (which can happen in older adults), that is a clue that your thirst mechanism may not be keeping up.
Fatigue, weakness, or low energy
When you are dehydrated, your blood volume can drop and your muscles may not get the same oxygen and nutrient delivery. High sodium itself can also affect how cells handle water, which can contribute to feeling “run down.” This symptom is not specific, so it matters whether it came with other dehydration signs like dark urine or rapid heart rate.
Headache, dizziness, or feeling lightheaded
Fluid shifts and lower circulating volume can trigger headaches or dizziness, especially when standing up. If you are on diuretics or have been sick, these symptoms can signal that your fluid balance is off. Severe dizziness, fainting, or confusion should be treated as urgent.
Less frequent urination or very dark urine
Your kidneys try to conserve water when sodium is high, so you may urinate less and the urine may look darker. The exception is diabetes insipidus or osmotic diuresis from very high glucose, where you can have high sodium and still urinate a lot. That “high sodium + high urine volume” combination is a key pattern to bring to your clinician.
Confusion or irritability (more severe cases)
When sodium rises significantly, water can move out of brain cells, which can affect mental status. Confusion, agitation, or unusual sleepiness is more likely when sodium is well above the reference range or rises quickly. This is not a “wait and see” symptom—especially in older adults.
How to Bring Sodium Back Toward Normal
Rehydrate steadily with water first
For many people, mild high sodium improves when you replace the water you are missing. Sip regularly over several hours rather than chugging a large amount at once, and pay attention to urine color and frequency as practical feedback. If you have heart failure, kidney disease, or a fluid restriction, ask your clinician what “safe rehydration” looks like for you before increasing fluids.
Replace fluids during illness (and stop the losses)
If vomiting or diarrhea is driving the problem, the priority is to control the illness and replace fluids as you go. Oral rehydration solutions can be helpful when you are losing a lot of fluid, but they still need to be used thoughtfully because some products contain significant sodium. If you cannot keep fluids down or you feel confused or very weak, you may need medical evaluation for IV fluids and monitoring.
Review diuretics and “drying” meds with your prescriber
Do not change prescription doses on your own, but do bring your sodium result to the clinician who manages your diuretics, lithium, or other relevant medications. The fix may be adjusting timing, dose, or adding monitoring (like daily weights and repeat electrolytes). Medication-related hypernatremia is often about the balance between water loss and intake, not about eating too much salt.
If you exercise in heat, plan fluids and weigh in/out
A simple way to estimate sweat losses is to weigh yourself before and after a long workout. If you are consistently finishing lighter, you are not replacing enough fluid, which can push sodium up. Aim to replace most of the lost weight with fluids over the next few hours, and be cautious with very salty supplements unless you also replace water.
Retest when you are back to baseline
Because sodium can shift with a single day of dehydration, a repeat test is often the fastest way to separate a temporary issue from a persistent one. Retesting also lets you check the pattern with chloride, potassium, and kidney function, which helps pinpoint the cause. If your sodium is significantly elevated (for example, ≥150 mmol/L) or you have neurologic symptoms, do not wait for a routine retest—get evaluated.
Other Tests That Give Context to High Sodium
If you're dealing with symptoms of high sodium, these labs can show whether a hidden imbalance is driving it, not just a rough guess. Start with Sodium:Potassium Ratio, Creatinine, and Bun/Creatinine Ratio: add the markers that match how you feel, test at a Quest location, and walk into your next visit with results in hand. Most of these tests start from $13.99.
Sodium:Potassium Ratio
This ratio is increasingly recognized as an important marker for cardiovascular risk and hypertension. A high sodium-to-potassium ratio is associated with increased blood pressure and cardiovascular disease risk. Optimizing this ratio through diet (reducing sodium, increasing potassium) can improve cardiovascular health. The Sodium to Potassium ratio reflects electrolyte balance and has implications for cardiovascular health, blood pressure regulation, and cellular function.
Creatinine
$13.99
Creatinine is a waste product of muscle metabolism that is filtered by the kidneys and serves as the primary marker of kidney function. In functional medicine, creatinine levels reflect not only kidney health but also muscle mass and protein metabolism. Elevated creatinine indicates reduced kidney filtration capacity, while very low levels may indicate muscle wasting or poor protein intake. Creatinine is used to calculate eGFR and helps assess long-term kidney health and detoxification capacity. Creatinine measures kidney filtration capacity and muscle metabolism, serving as the primary indicator of kidney health and detoxification.
Bun/Creatinine Ratio
$16.99
This ratio helps differentiate between prerenal (dehydration, heart failure), intrinsic renal, and postrenal (obstruction) causes of elevated kidney markers. A high ratio often indicates dehydration or upper GI bleeding, while a low ratio may suggest liver disease or malnutrition. It's essential for accurate assessment of kidney function and fluid status. The BUN to Creatinine ratio compares two kidney function markers to help identify the cause of kidney dysfunction and assess hydration status.
Pro Tips
If your sodium is only slightly high, avoid alcohol and very intense exercise for 24 hours before a retest, because both can increase water loss and concentrate your blood.
On the morning of your blood draw, drink a normal amount of water (unless you are on a fluid restriction) so the result reflects your baseline rather than an unusually dry start to the day.
If you take a diuretic, ask your clinician whether your lab should be drawn before your dose, after your dose, or at a consistent time each time—timing can change electrolyte readings.
Write down recent vomiting/diarrhea, fever, long workouts, sauna use, or heat exposure in the 48 hours before the test; that timeline often explains a temporary sodium bump.
Compare sodium with creatinine and BUN (if available): a “concentrated” pattern supports dehydration, while a different pattern may point to medication or hormone-related causes.
Retest sodium with potassium, chloride, and kidney markers at Quest
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When to see a doctor
If your sodium is ≥150 mmol/L, if it stays above 145 mmol/L on repeat testing, or if you have confusion, severe weakness, fainting, or signs of significant dehydration (very low urine output, rapid heartbeat), contact a clinician promptly or seek urgent care. Persistent hypernatremia can reflect ongoing fluid loss, medication effects, uncontrolled diabetes, or a water-balance disorder like diabetes insipidus, and it is safest to correct it with guidance. Tracking sodium alongside potassium, chloride, and creatinine helps put the result in context instead of guessing from a single number.
Frequently Asked Questions
Is high sodium in a blood test dangerous?
It can be, but risk depends on how high it is and how fast it rose. Mild elevations (for example 146–148 mmol/L) are often from dehydration and improve with rehydration, while higher levels (especially ≥150 mmol/L) can affect the brain and require prompt medical guidance. The safest next step is to look for dehydration or medication triggers and confirm with a repeat test.
Can dehydration cause high sodium?
Yes—this is the most common reason. When you lose water (or do not drink enough), sodium becomes more concentrated in your blood even if you did not eat extra salt. If you also have dark urine, thirst, or a higher BUN/creatinine pattern, dehydration becomes even more likely.
Does eating salty food cause high sodium in blood work?
Usually not by itself, because healthy kidneys can excrete extra sodium and keep blood sodium in a tight range. High sodium on labs more often reflects water balance (too little water) than salt intake. That said, very high salt intake can worsen thirst and fluid shifts, especially if you also have kidney disease or heart failure.
How quickly can sodium go back to normal?
If the cause is mild dehydration, sodium can improve within hours to a day once you rehydrate and stop ongoing losses. If the cause is ongoing (diuretics, uncontrolled diabetes, diabetes insipidus, or continued GI losses), it may stay high until the underlying issue is addressed. A repeat test when you feel back to baseline is often the clearest way to confirm.
What should I do if my sodium is 146 or 147?
That is a mild elevation for many labs, and dehydration is a common explanation. Review recent fluid intake, illness, sweating, and medications, then rehydrate normally (unless you have a fluid restriction) and consider a repeat sodium with potassium, chloride, and kidney function. If you feel confused, faint, or very weak, or if the number is rising, get medical advice sooner.
Research and guidelines
Verbalis JG, et al. Diagnosis, evaluation, and treatment of hyponatremia: expert panel recommendations. Am J Med. 2013.
Adrogué HJ, Madias NE. Hypernatremia. N Engl J Med. 2000.
UpToDate topic: Evaluation and management of hypernatremia in adults.
