When people hear “low sodium,” they often think it’s just about eating less salt. But hyponatremia (low sodium in the blood) is usually more about water balance—how your body is holding onto, losing, or shifting fluids. That’s one reason it can show up in people with diabetes mellitus, especially during illness, hospitalization, medication changes, or big swings in blood sugar.
In this article, we’ll build the full picture step by step—starting with what hyponatremia is and why it matters clinically.
What Is Hyponatremia?
Hyponatremia means the sodium concentration in your blood is lower than normal. In most labs, it’s generally defined as a serum sodium < 135 mEq/L (or mmol/L).
Why sodium matters (in plain language)
Sodium is one of the main “electrolytes” in your bloodstream. Its concentration helps regulate:
- How water moves between your bloodstream and your cells
- Nerve signaling (including brain function)
- Muscle function (including the heart)
Here’s the key concept: in many cases, hyponatremia doesn’t happen because the body has no sodium at all—it happens because there’s too much water relative to sodium, diluting the sodium concentration.
How hyponatremia is commonly classified
Clinicians often describe hyponatremia by severity because symptoms and urgency can change quickly as sodium falls:
- Mild: about 130–135 mEq/L
- Moderate: about 125–130 mEq/L
- Severe (or “profound” in some guidelines): < 125 mEq/L
(Exact cutoffs can vary slightly by guideline and lab, but these ranges are widely used.)
Symptoms: from subtle to dangerous
Hyponatremia can be silent when mild or gradual. But as it worsens—or when it drops quickly—symptoms often become neurological. That’s because shifts in sodium concentration can pull water into brain cells, contributing to brain swelling (especially in acute cases).
Possible symptoms include:
- Nausea, vomiting
- Headache
- Muscle cramps or weakness
- Fatigue, low energy, drowsiness
- Confusion, irritability, trouble concentrating
- Seizures, reduced consciousness, coma (more likely in severe or fast-onset cases)
Safety note: If someone has serious symptoms like seizures, severe confusion, or loss of consciousness, that’s an emergency situation and needs urgent medical care.
Acute vs chronic hyponatremia (why timing changes risk)
Doctors also think about hyponatremia in terms of how fast it developed:
- Acute hyponatremia: develops quickly (often discussed as within ~48 hours)
- Chronic hyponatremia: develops more slowly, over days to longer
This matters because the brain can partially adapt to slow changes—but it has less time to adapt to fast drops, which can increase the risk of severe neurological symptoms.
A common misunderstanding: “low sodium” isn’t always “low salt intake”
It’s understandable to assume hyponatremia means “I didn’t eat enough salt.” Sometimes sodium intake plays a role, but clinically, hyponatremia is more often linked to things like:
- Medications (including some diuretics)
- Hormone signaling that increases water retention (like SIADH—excess ADH/vasopressin effect)
- Kidney, heart, or liver problems
- Large fluid intake or IV fluids in certain settings
This is especially relevant in diabetes, where blood sugar changes can strongly influence fluid shifts—something we’ll unpack in later sections.
Understanding Diabetes Mellitus
To understand why hyponatremia can show up in diabetes, it helps to zoom out and look at what diabetes mellitus actually does to fluid balance, kidney function, and hormone signals.
A quick, practical overview of diabetes (Type 1 vs Type 2)
Diabetes mellitus is a group of metabolic conditions where blood glucose (blood sugar) stays higher than it should because the body doesn’t make enough insulin, doesn’t use insulin well, or both.
The two most common types are:
- Type 1 diabetes (T1D): the immune system damages insulin-producing beta cells in the pancreas, so the body makes little to no insulin. People with T1D need insulin to survive.
- Type 2 diabetes (T2D): the body becomes resistant to insulin and, over time, may also produce less insulin than needed. This is the most common form globally.
A small but important clarity point: diabetes mellitus is different from diabetes insipidus, which is a rare disorder of water regulation involving ADH (vasopressin). They sound similar but behave very differently in the body.
How diabetes affects fluid and electrolyte balance
When blood glucose rises high enough, the kidneys start spilling glucose into the urine. Glucose in the urine pulls water with it—this is osmotic diuresis. In plain terms: high sugar can make you urinate more, and that increased urination can drag fluids (and electrolytes) out of the body.
That’s why classic uncontrolled diabetes symptoms often include:
- Frequent urination (polyuria)
- Increased thirst (polydipsia)
- Dehydration, especially during illness, poor intake, or missed medications
In severe hyperglycemia—such as hyperosmolar hyperglycemic state (HHS)—the combination of extreme glucose levels and osmotic diuresis can cause significant volume depletion (dehydration) and shifts in electrolytes.
This fluid–electrolyte stress is one of the key “setup conditions” for sodium problems later, including hyponatremia (and sometimes hypernatremia, depending on water losses and replacement).
Why kidneys matter so much here
Your kidneys aren’t just “filters.” They constantly adjust:
- how much water you keep vs. lose
- how much sodium and other electrolytes you reabsorb vs. excrete
Diabetes is also a leading cause of chronic kidney disease (often called diabetic kidney disease). When the kidneys become damaged over time, their ability to fine-tune water and electrolyte handling can become less predictable—especially during dehydration, infection, medication changes, or hospitalization.
The relevance of insulin to sodium retention (a detail that matters later)
Insulin doesn’t only move glucose into cells—it also has effects in the kidney. Research shows insulin can increase sodium reabsorption along different parts of the nephron (the kidney’s tubule system).
Mechanistically, one pathway involves insulin stimulating transporters like NHE3 (sodium–hydrogen exchanger 3) in the proximal tubule, which supports sodium reabsorption.
Why mention this now? Because when insulin levels change (or when insulin is given during treatment), water and sodium can shift—and in the “wrong” context (like dehydration, excess free water intake, kidney impairment, or certain medications), those shifts can contribute to abnormal sodium readings.
Also worth noting: some modern diabetes medications (for example, SGLT2 inhibitors) intentionally increase glucose loss in urine and can have mild diuretic/natriuretic effects—another reason hydration and electrolytes can become more relevant in some patients.
How Are Diabetes and Hyponatremia Connected?
Diabetes can set up several different pathways that make a sodium result come back low. Sometimes it’s true hyponatremia (the blood really is too diluted with water). Other times, it’s a “looks-low” sodium caused by high glucose or lab measurement effects—important distinctions because the management approach is different.
Causes of Hyponatremia in Diabetics
Below are the most common mechanisms clinicians look for in people with diabetes.
1) Osmotic shifts from hyperglycemia (a low sodium reading that can happen fast)
When blood glucose is very high, glucose stays largely in the bloodstream (outside cells) and pulls water out of cells into the blood. That extra water in the bloodstream can dilute the measured sodium, producing hypertonic (translocational) hyponatremia.
Because of this effect, many teams calculate a “corrected sodium” to estimate what sodium would be if glucose were normal. There isn’t one universal correction factor—different references use slightly different adjustments:
- A commonly used approach is roughly +1.6 mEq/L sodium for every 100 mg/dL glucose above normal.
- Some clinical data suggest the sodium drop can be larger at higher glucose levels (often summarized as ~2.4 mEq/L per 100 mg/dL in severe hyperglycemia).
The practical takeaway: don’t interpret sodium in isolation when glucose is very high—you almost always want sodium + glucose + osmolality together to understand what’s happening.
2) Osmotic diuresis from hyperglycemia (true losses + “replacement mismatch”)
High glucose can cause osmotic diuresis—you pee out glucose and water, and you can also lose electrolytes along the way. This can leave someone volume depleted (dehydrated), but the sodium level can still read low depending on what they drink/receive to replace fluids (for example, lots of free water without enough electrolytes).
This is one reason sodium can behave in “non-intuitive” ways during DKA or HHS: the body is simultaneously dealing with glucose-driven water shifts and large fluid/electrolyte losses.
3) ADH-driven water retention (illness stress + SIADH patterns)
When the body is under stress—pain, nausea, infection, surgery—it may release more ADH/vasopressin, which tells the kidneys to hold onto water. Holding onto “extra water” without matching sodium can contribute to dilutional (hypotonic) hyponatremia.
Separately, many hospitalized patients develop SIAD / syndrome of inappropriate antidiuresis, where ADH activity is “too high for the situation,” leading to euvolemic hyponatremia (low sodium without obvious fluid overload or dehydration). This can be triggered by pulmonary or CNS disease, medications, and the hospital/post-op setting—situations that are unfortunately common among people with diabetes when complications occur.
4) Medications common in diabetes care (especially diuretics)
Many people with diabetes also manage hypertension, heart disease, or kidney disease, and that often means medications that can affect sodium balance.
A major example is thiazide diuretics (commonly used for blood pressure). Thiazides are a well-known cause of hyponatremia, particularly in older adults and in the first weeks after starting or changing the dose.
(Other drugs—like some antidepressants—can also contribute via SIADH pathways, but thiazides are a classic, high-yield one to recognize.)
5) Hypoglycemia treatment + fluid choices (oral or IV)
Treating low blood sugar usually focuses on glucose replacement, but in some settings—especially hospitals—IV fluids and dextrose solutions can add “electrolyte-free water” once the glucose is metabolized, which can contribute to dilutional hyponatremia if not monitored carefully.
6) Iatrogenic overhydration during hospitalization (the “too much free water” problem)
People with diabetes are more likely to be hospitalized for infections, surgeries, or hyperglycemic crises—situations where IV fluids are common. Hyponatremia can be iatrogenic when a patient receives too much free water (often via hypotonic IV fluids) relative to sodium needs, especially if ADH is already high from illness stress.
This is why major guidance for DKA/HHS emphasizes careful monitoring of sodium, glucose, and osmolality, and generally begins resuscitation with isotonic saline, adjusting as labs evolve.
Pseudohyponatremia in Diabetics
“Pseudohyponatremia” means the lab reports a low sodium value, but the sodium in the plasma water is actually normal—the number looks low due to the way the sample was measured.
What it is and why it happens
Some lab methods (notably indirect ion-selective electrodes, which dilute the sample) can read sodium falsely low when the blood has an unusually high “solid” fraction—most commonly from:
- Very high triglycerides (severe hypertriglyceridemia)
- Very high proteins
This can matter in diabetes because severe hyperglycemia (and sometimes DKA) can be associated with marked lipid abnormalities in certain patients.
How lab measurements can mislead
- Indirect ISE (common in many chemistry analyzers) is the setup where pseudohyponatremia is most likely.
- Direct ISE (often used in blood gas machines) does not dilute the sample and is less affected by high lipids/proteins.
How to differentiate true vs false hyponatremia (a practical mental checklist)
Clinicians usually sort this out by pairing sodium with serum osmolality and the clinical context:
- Hyperglycemia-related hyponatremia: sodium low with elevated tonicity/osmolality (because glucose is an effective osmole).
- True hypotonic hyponatremia: low sodium with low serum osmolality, then further classified by volume status and urine studies.
- Pseudohyponatremia: low sodium with normal serum osmolality, especially if triglycerides or proteins are very high, and/or if a direct ISE gives a higher sodium than the chemistry analyzer.
Symptoms and Complications
Hyponatremia can look “vague” at first—especially in someone with diabetes, where fatigue, dizziness, and mental fog can also come from high/low blood sugar, dehydration, infections, or medication effects. The key is to recognize patterns that suggest sodium (and water balance) is part of the picture, not just glucose.
Common symptoms (often mild to moderate)
These are the kinds of symptoms people may brush off as stress, poor sleep, or “my diabetes acting up”:
- Fatigue, lethargy, low energy
- Muscle cramps or generalized weakness
- Subtle mood/mental changes like irritability, feeling “off,” or trouble focusing
Clinically, these symptoms happen because low sodium can disrupt how nerves and muscles function, and because water shifts can affect brain cells—particularly if sodium drops quickly.
Red-flag symptoms (more severe or rapidly developing hyponatremia)
If sodium drops to very low levels or falls quickly, symptoms can become neurological and urgent:
- Marked confusion, severe drowsiness, inability to stay awake
- Seizures
- Coma
Severe neurologic symptoms are treated as a medical emergency because acute hyponatremia can be associated with dangerous brain swelling and worsening mental status.
Complication: Falls and injury risk (especially in older adults with diabetes)
In older adults, even “milder” hyponatremia has been linked in clinical research to gait instability, attention problems, and increased falls—and diabetes can add extra fall risk through neuropathy, vision changes, and blood pressure variability.
Complication: Neurological harm from correcting sodium too fast (CPM / ODS)
One of the most important complications isn’t just the low sodium itself—it’s over-correcting it too quickly, especially if hyponatremia has been present for more than a day or two.
- Rapid correction can trigger osmotic demyelination syndrome (ODS), historically associated with central pontine myelinolysis (CPM), which can cause severe, sometimes irreversible neurological problems.
This is why hyponatremia management is usually careful and stepwise, with frequent lab monitoring—particularly in hospitalized or medically complex patients (a group that includes many people living with diabetes).
Diagnosis and Medical Evaluation
Evaluating hyponatremia in someone with diabetes isn’t just about the sodium number. Clinicians typically take a step-by-step approach to figure out:
- Is the sodium truly low or falsely low?
- If true hyponatremia: What’s the tonicity?
- What’s the volume status?
- What’s the likely cause—and how urgent is it to treat?
Here’s how that often plays out in practice.
Lab tests commonly ordered
- Serum sodium (basic metabolic panel or electrolyte panel)
- Blood glucose (to help calculate corrected sodium)
- Serum osmolality
- Urine sodium and urine osmolality
- Kidney function (BUN, creatinine, eGFR)
- Lipid panel (if pseudohyponatremia is suspected)
- Thyroid and adrenal labs, in some persistent or unexplained cases
These tests help classify the type of hyponatremia (e.g. hypotonic, hypertonic, isotonic), and guide whether the issue is due to fluid overload, fluid loss, or abnormal water retention.
Clinical assessment of volume status
Doctors also look for physical clues of fluid status:
- Dry mouth, skin turgor, blood pressure changes → dehydration
- Swelling, shortness of breath, crackles in lungs → fluid overload
- No obvious signs → often the pattern seen in SIADH (euvolemic hyponatremia)
This is sometimes tricky—especially in older adults or people with multiple chronic conditions—but still a key part of narrowing down causes.
Prevention and Monitoring
Preventing hyponatremia in diabetes is mostly about good overall management and early recognition of risk situations. There’s no one-size-fits-all rule, but here are the strategies most often emphasized by healthcare teams.
For people living with diabetes:
- Stay hydrated—but not excessively. Avoid large volumes of free water unless advised by a provider.
- Monitor blood sugar regularly, especially during illness, medication changes, or if using insulin.
- Understand your medications, especially if you take diuretics, SGLT2 inhibitors, or other drugs that affect fluid/electrolyte balance.
- Report symptoms like confusion, severe fatigue, or unsteady walking—don’t assume it’s “just high sugar.”
During hospital care or illness:
- Ask about your labs. Understanding how sodium, glucose, and kidney function are trending can help avoid surprises.
- Speak up about fluid intake. If you’re getting IV fluids or drinking a lot but not urinating much, let your team know.
- Recheck labs after treatment. Changes in glucose, insulin, fluids, or meds can shift sodium and water balance—especially in DKA or HHS recovery phases.
Conclusion: What This Means for You
If you or someone you care about has diabetes, it’s worth knowing that hyponatremia isn’t just a “salt problem”—it’s often a signal that water balance, glucose control, kidney function, or medication effects are interacting in complex ways.
Hyponatremia can be:
- Dilutional, from too much water relative to sodium
- Osmotic, from glucose pulling water out of cells
- Iatrogenic, from how we treat illness, fluids, or low sugar
- Misleading, due to lab artifacts like pseudohyponatremia
Because diabetes influences nearly all the systems that regulate sodium—kidneys, hormones, hydration, glucose, and medication use—it makes hyponatremia both more likely and more complicated to assess.
That’s why managing diabetes isn’t just about blood sugar—it’s about understanding your whole fluid and electrolyte picture, especially during stress, sickness, or hospital care.
If you’re feeling “off,” confused, very fatigued, or unusually weak—especially during times of illness, dehydration, or medication changes—it’s worth asking your healthcare team to look at your sodium and osmolality, not just your glucose.
Understanding the connection between diabetes and hyponatremia won’t prevent every complication—but it arms you with knowledge to notice problems earlier, speak up more confidently, and support a safer recovery when challenges come up.
Natural support like buah merah or ant nest plant may be part of the picture, but it’s not a substitute for medical guidance.
