Overview

blood test

The following information breaks blood tests into three groups: nutrients, metabolic and miscellaneous, and hormones. Ask your doctor to order their standard panel first. Then add specific tests when relevant.

Nutrients

nutrients

Iron studies

  • What to ask for: ferritin, serum iron, transferrin, and TIBC/GIBC.
  • Why it matters: low ferritin links with fatigue, brain fog, and poor exercise tolerance. It’s common and very fixable.

Vitamin B12 and folate

  • Why it matters: support energy, red blood cell formation, and neurological health.
  • Who to watch: plant-based eaters and older adults, since B12 absorption often declines with age

Vitamin D

  • Why it matters: supports bone health, immunity, and mood.
  • When to check: winter, office-bound routines, or lower time outdoors.

Magnesium and calcium (context)

  • Caveat: blood levels don’t reflect intake well due to homeostasis.
  • Example: the body can pull calcium from bone to keep blood levels in range, or reduce absorption when high. Out-of-range values often suggest other issues (e.g., kidneys), not diet alone.

Zinc

  • Why it matters: immune function, wound healing, and hair growth.
  • When to add: lower intake or restrictive diets.
  • Supplement caution: long-term high doses (e.g., 50 mg/day year-round) may reduce copper by competing for absorption. Short-term higher doses can be useful but monitor duration.

Metabolic and Miscellaneous

blood lipids

Glucose control

  • Tests: fasting glucose and HbA1c.
  • Why it matters: screens insulin sensitivity, type 2 diabetes risk, and longer-term blood sugar control.
  • Note: HbA1c reflects roughly a three-month average because it tracks red blood cells.

Blood lipids

  • What to watch: total cholesterol and triglycerides, with nuance around LDL and prevention targets.
  • Ranges often discussed: 4.0, 5.5, and 6.0 mmol/L. Some clinicians flag “high” at 5.5; others at 6.0. Primary prevention targets sit lower than secondary prevention.
  • Takeaway: keeping LDL lower reduces cardiovascular risk; this explains why statins often drive LDL very low.

Liver function

  • Tests: ALT, AST, GGT; sometimes ALP and bilirubin.
  • Why it matters: helps flag inflammation and potential fatty liver, and can guide weight-loss support when needed.

Kidney function

  • Tests: creatinine, urea, and eGFR.
  • Tip: eGFR usually derives from creatinine on standard reports, so creatinine changes drive the estimate.

Training effects on labs

  • Heavy training within a few days can elevate liver enzymes.
  • More muscle mass or a hard session can raise creatinine, since creatine breaks down to creatinine.
  • For the most accurate snapshot, deload or even take a week off before testing; some markers can stay elevated for up to a week after a single hard session in non-lifters.

C-reactive protein (CRP)

  • What it shows: systemic inflammation.
  • How it behaves: very low at baseline, extremely high with acute illness, and modestly raised with chronic disease.
  • Useful question: when someone says they’re “inflamed,” has CRP actually been measured?

Hormones

hormomes

Thyroid

  • Tests: TSH, free T4, and free T3.
  • Why it matters: these drive metabolism, energy, and weight regulation.
  • Conditions: hypothyroidism (down-regulated thyroid) and hyperthyroidism (up-regulated).
  • Practical note: when thyroid hormones are brought back into range (e.g., with medication), metabolic rate typically looks similar to people without hypothyroidism. Doses often need ongoing adjustment, so periodic testing helps.

Female sex hormones

  • Tests: estradiol (estrogen), progesterone, FSH, and LH.
  • Why it matters: informs menstrual cycle status, menopause, and even bone health signals.
  • Reading results: reference ranges often vary by cycle phase; knowing the tested phase is important. Out-of-range across all phases is more concerning.

Testosterone

  • Measures: total and free testosterone.
  • When to check in women: part of a PCOS work-up when symptoms suggest elevated androgens.
  • When to check in men: not routine for everyone; consider if symptoms point to low testosterone. From there, options include nutritional approaches or discussing hormone therapy with a clinician.

Key Takeaways

  • Start with your doctor’s standard panel, then add targeted tests based on your context, symptoms, and goals.
  • Time your blood draw with training in mind to reduce misleading results.
  • Re-test when treatments or life circumstances change, since ranges and needs can shift.