What each biomarker tells a runner
Objective data for smarter training decisions.
Electrolytes
Sodium, potassium, chloride, bicarbonate
Electrolytes control fluid balance, nerve signals, muscle contraction, and your heart's rhythm. Every mile you sweat, you lose them.
How we use it: We use your electrolyte results to guide how we adjust water and electrolyte intake for training and racing. A low-normal sodium may mean your race plan needs more sodium with your fluids. A sodium that drops after long runs can be an early sign of drinking too much plain water.
Know this: More water is not always better. Drinking well beyond thirst during long events can dilute blood sodium to dangerous levels (exercise-associated hyponatremia).
Potassium and kidney function
BUN, creatinine, eGFR
Your kidneys filter waste and keep fluid and electrolytes in balance. Long, hard efforts put real demand on them, especially in heat or when you are behind on fluids.
How we use it: We use kidney markers together with electrolytes to guide hydration and electrolyte planning. During extreme exertion, muscle tissue can break down (rhabdomyolysis), releasing potassium into the blood and straining the kidneys. Knowing your baseline potassium and kidney function before a training block helps you and your clinician spot risk factors you can address, such as training dehydrated or starting with a potassium level that is already on the high side.
Know this: Creatinine runs higher in muscular athletes and right after hard training, so we interpret it in context.
CO2 (bicarbonate)
Your acid-base buffer
Most of the CO2 on a metabolic panel is bicarbonate, your body's main buffer against acid. Intervals, hills, and race surges produce acid, including the lactic acid build-up you feel as the burn.
How we use it: We look at your CO2 to understand your current acid-base (pH) buffering status and how well your body may handle the acid load of high-intensity work.
Know this: This test reflects buffering capacity. It does not directly measure blood pH or lactate.
Total protein and albumin
Fueling and nutritional status
Endurance training breaks muscle down. Recovery builds it back, but only if you are fueling well.
How we use it: We look at protein and albumin as part of the picture of how you have been fueling and your overall nutritional status.
Know this: Hydration, inflammation, and liver or kidney health also affect these numbers, so they are not a standalone measure of protein intake.
hs-CRP
Inflammation
High-sensitivity C-reactive protein is a sensitive marker of inflammation made by your liver.
How we use it: We use hs-CRP to see whether you may be dealing with acute or chronic inflammation that could help explain nagging fatigue, slow recovery, lingering illness, or an underlying problem worth evaluating. In the right clinical context, hs-CRP is also part of assessing cardiovascular risk.
Know this: A hard workout, recent injury, or a cold can raise hs-CRP for a few days. If it is high, retest when rested and well.
Also on your panel
Glucose, calcium, liver markers
Glucose shows how your body regulates blood sugar. Calcium supports muscle contraction, nerve signaling, and heart rhythm. AST, ALT, alkaline phosphatase, and bilirubin reflect liver and metabolic health.
How we use it: Together they round out your metabolic baseline before you ask more of your body.
Know this: AST and ALT can rise temporarily after hard runs, another reason to test rested.
