Sodium, potassium, calcium, phosphorus, magnesium, bicarbonate. The kidney regulates all of them, minute to minute, and when it falters the numbers move.
Most electrolyte abnormalities are found on a routine blood test in someone who feels fine. Some are emergencies. Telling those apart is the work.
The thing worth understanding
An abnormal electrolyte is a symptom, not a diagnosis.
Low sodium is almost never a sodium problem — it is a water problem, and treating it with salt misunderstands the physiology. High potassium is often blamed on a kidney-protective medication that should not be stopped. A low bicarbonate that looks trivial on paper accelerates bone and muscle loss.
Each of these gets managed wrong in predictable ways, and the corrections have consequences. Sodium raised too quickly causes permanent neurologic injury. Potassium treated by abandoning an ACE inhibitor costs the patient the drug protecting their kidney.
The number tells you something is wrong. It does not tell you what, and it does not tell you what to do.
| Electrolyte | Too low | Too high |
|---|---|---|
| Sodium | Confusion, falls | Thirst, agitation |
| Potassium | Weakness, cramps | Dangerous heart rhythms |
| Calcium | Tingling, spasms | Fatigue, kidney stones |
Where to go from here
Hyponatremia — low sodium. Why it is a water problem, why the correction rate matters more than the target, and what osmotic demyelination is.
Hyperkalemia — high potassium. When it is an emergency, and why stopping the ACE inhibitor is usually the wrong trade.
Metabolic Acidosis — low bicarbonate. The abnormality that looks minor and is not.
chronic kidney disease (CKD) Mineral & Bone Disorder — calcium, phosphorus, and parathyroid hormone in kidney disease.
Why a nephrologist
The kidney is the organ that sets these values. An electrolyte abnormality in someone with kidney disease is rarely isolated, and it is rarely random — it points at a mechanism, and the mechanism determines the treatment.
If a lab result was flagged and nobody explained why it happened, that is the question worth answering.