Kidney & Electrolytes

Creatinine is a routine blood test, and many laboratories now automatically report a kidney-function estimate (eGFR) calculated from it on your lab report.

Chronic kidney disease is far more common than most people realise. A Global Burden of Disease analysis estimated that in 2017 there were 697.5 million cases of all-stage CKD worldwide, a global prevalence of 9.1%.

The CO2 blood test is easy to overlook on a routine panel, yet its “normal range” varies considerably between laboratories.

Chloride is rarely at the centre of medicine in the way sodium and potassium are. Its concentration does matter in some clinical situations, intravenous fluid correction of dehydration in children being one example.

The anion gap can appear on chemistry reports, sometimes without explanation.

The basic metabolic panel (BMP) is a routine set of blood chemistry tests used in health checks, emergency departments and hospital wards.

A flagged BUN creatinine ratio can be worrying, particularly because the usual explanation — “a high ratio means you are dehydrated” — sounds simple enough to act on.

When an athlete’s urine dipstick comes back positive for protein, the immediate instinct can be alarm. Protein in urine is, after all, one of the classic signs of kidney disease.

In clinical practice, creatinine is usually the first-line test used to assess kidney function. It is widely available, inexpensive, and often included automatically in standard blood panels.

eGFR (estimated glomerular filtration rate) is the standard marker of kidney filtration capacity, calculated from serum creatinine using one of several mathematical formulas.

In clinical practice, I often see gout and elevated uric acid mentally grouped with lifestyle-related metabolic disease.

Aldosterone is a clinically important hormone. Many medications that affect blood pressure also influence aldosterone physiology, and aldosterone sits behind several key mechanisms in fluid balance, electrolyte regulation, and cardiovascular control.

Serum phosphate in athletes may provide clinically relevant information in blood work when interpreted in context. Phosphate plays important roles in ATP-related metabolism, red-cell energetics, and bone mineralisation.

If a urine sample is collected from an athlete immediately after exercise, it is fairly common to detect protein in the sample.

Chloride is often an overlooked electrolyte in clinical practice. When electrolytes are discussed, the focus is typically on sodium and potassium, with chloride receiving considerably less attention.

Potassium is the body’s principal intracellular cation, with roughly 98% of total body stores residing within cells and only 2% in the extracellular fluid .

In the general population, sodium intake is often higher than necessary, and reducing excess salt is commonly recommended due to its association with cardiovascular risk.

Athletes represent a distinct population in whom creatinine measurements are frequently influenced by factors such as greater muscle mass, training load, and supplementation.

Electrolytes in athletes play a central role in athletic physiology, and exercise does affect the body’s electrolyte balance.

Like many of my patients, if you’ve had blood tests done and your report says “anion gap low”, it’s very normal to feel anxious.