Blood panels are the single most objective window into your health. They don't lie, they don't have opinions, and they catch problems months or years before symptoms show up. But most people get their results back, see a column of numbers, and have no idea what they're looking at.
Here's what each marker actually tells you, and the difference between "normal" and optimal.
Metabolic markers
Fasting glucose
What it measures: Blood sugar levels after an overnight fast (8-12 hours).
Lab reference range: 70-100 mg/dL
Optimal range: 72-90 mg/dL
Why it matters: Elevated fasting glucose is an early warning sign of insulin resistance and pre-diabetes. By the time you're diagnosed with type 2 diabetes (126+ mg/dL), metabolic dysfunction has been building for years. Catching levels in the 95-110 range gives you time to intervene with lifestyle changes before medication is needed.
HbA1c (Hemoglobin A1c)
What it measures: Your average blood sugar over the past 2-3 months. It reflects how much glucose has attached to your red blood cells.
Lab reference range: Below 5.7% (normal), 5.7-6.4% (pre-diabetic), 6.5%+ (diabetic)
Optimal range: Below 5.3%
Why it matters: HbA1c is more informative than a single fasting glucose reading because it captures the bigger picture. It's not affected by what you ate yesterday. A value of 5.5% isn't "diabetic," but it suggests blood sugar regulation is starting to slip, and it's worth investigating further with fasting insulin.
Fasting insulin
What it measures: How much insulin your pancreas is producing at rest.
Lab reference range: 2.6-24.9 uIU/mL
Optimal range: 2-6 uIU/mL
Why it matters: This is arguably the most important metabolic marker that most standard panels don't include. High fasting insulin, even with "normal" glucose, is a sign that your body is working overtime to keep blood sugar down. It's the earliest marker of insulin resistance, often elevated 10+ years before a diabetes diagnosis. If you only add one marker to your standard panel, make it this one.
Lipid panel
What it measures: Total cholesterol, LDL ("bad"), HDL ("good"), and triglycerides.
- Total cholesterol: Less important on its own. The ratio matters more.
- LDL: Lab reference: below 100 mg/dL. But particle size matters more than total LDL. Small, dense LDL particles are far more atherogenic than large, buoyant ones.
- HDL: Optimal: above 50 mg/dL for men, above 60 for women. Higher is generally better. HDL removes cholesterol from arterial walls.
- Triglycerides: Optimal: below 100 mg/dL. Elevated triglycerides (150+) are strongly associated with insulin resistance and cardiovascular risk. The triglyceride-to-HDL ratio is one of the best predictors of metabolic health, ideal is below 2:1.
Hormone markers
Total testosterone
Lab reference range: 300-1,000 ng/dL (men)
Optimal range: 500-900 ng/dL
Why it matters: This is the headline number, but it doesn't tell the whole story. A man with 400 ng/dL total T might feel fine if his free testosterone is adequate. Another man at 500 ng/dL might have symptoms if his SHBG is high and free T is low.
Free testosterone
What it is: The small fraction (~2-3%) of total testosterone that isn't bound to SHBG or albumin. This is the biologically active testosterone that your tissues can actually use.
Optimal range: 15-25 pg/mL (men)
Why it matters: Free T is often more clinically relevant than total T. You can have a "normal" total T of 500 but functionally low testosterone if your SHBG is elevated.
SHBG (Sex Hormone-Binding Globulin)
What it does: A protein that binds testosterone, making it unavailable for use. The more SHBG you have, the less free testosterone you have, even if total T looks fine.
Optimal range: 20-50 nmol/L (men)
Why it matters: High SHBG is common in aging men, men on certain medications, and those with liver conditions. It's the missing piece when total T looks "normal" but symptoms persist.
Estradiol (E2)
What it is: The primary form of estrogen. Yes, men have it too, and they need it. Estradiol is essential for bone density, cardiovascular health, and brain function. But too much is a problem.
Optimal range: 20-35 pg/mL (men)
Why it matters: In men, estradiol rises when testosterone is aromatized (converted) by fat tissue. Elevated E2 causes water retention, gynecomastia (breast tissue growth), mood changes, and further T suppression. It's especially important to monitor on TRT.
TSH (Thyroid-Stimulating Hormone)
Lab reference range: 0.4-4.0 mIU/L
Optimal range: 1.0-2.5 mIU/L
Why it matters: TSH is the first-line screen for thyroid function. A TSH above 2.5 isn't "hypothyroid" by lab standards, but many functional practitioners consider it suboptimal. Symptoms of subclinical hypothyroidism, fatigue, weight gain, cold sensitivity, brain fog, overlap significantly with low testosterone.
Cortisol
What it measures: Your primary stress hormone, produced by the adrenal glands.
Optimal morning range: 10-18 mcg/dL
Why it matters: Chronically elevated cortisol suppresses testosterone production, increases visceral fat storage, impairs sleep, and drives inflammation. A single morning cortisol isn't definitive (cortisol fluctuates throughout the day), but it's a useful screening tool.
DHEA-S
What it is: A precursor hormone produced by the adrenal glands. It's converted into testosterone and estrogen as needed.
Why it matters: DHEA declines with age. Low DHEA-S can contribute to fatigue, decreased libido, and poor recovery. It's a useful marker for overall adrenal function and hormonal reserve.
Inflammation and longevity markers
hs-CRP (High-Sensitivity C-Reactive Protein)
What it measures: Systemic inflammation.
Lab reference: Below 3.0 mg/L (low risk)
Optimal: Below 1.0 mg/L
Why it matters: Chronic low-grade inflammation is a driver of cardiovascular disease, metabolic syndrome, cancer, and neurodegeneration. hs-CRP is the most widely used inflammatory biomarker. If yours is above 1.0, it's worth investigating the source, excess body fat, poor diet, chronic stress, poor sleep, or an underlying condition.
Homocysteine
What it measures: An amino acid that, when elevated, damages blood vessel walls and increases cardiovascular risk.
Optimal: Below 8 umol/L
Why it matters: Elevated homocysteine is an independent risk factor for heart attack and stroke. It's often easily correctable with B vitamins (B6, B12, folate). This marker is underordered and underappreciated.
Vitamin D (25-hydroxyvitamin D)
Lab reference: 30-100 ng/mL
Optimal: 50-80 ng/mL
Why it matters: An estimated 42% of American adults are vitamin D deficient. Vitamin D is technically a hormone, not a vitamin, and it influences immune function, bone density, mood, testosterone production, and cancer risk. Most people need supplementation to reach optimal levels, especially if they live in northern latitudes or work indoors.
Blood health
CBC (Complete Blood Count)
What it measures: Red blood cells (oxygen delivery), white blood cells (immune function), and platelets (clotting).
Why it matters: Anemia (low red cells) causes fatigue and poor exercise tolerance. Elevated white cells can signal infection or chronic inflammation. Low platelets affect clotting. The CBC is a foundational screening test included in almost every panel.
Hematocrit
What it measures: The percentage of your blood volume that's red blood cells.
Optimal: 38-50% (men)
Why it matters: Especially critical for men on TRT. Testosterone stimulates erythropoiesis (red blood cell production). If hematocrit rises above 54%, blood becomes too viscous, increasing the risk of clots, stroke, and heart attack. TRT patients should have hematocrit checked every 3-6 months. If it's high, dose reduction or therapeutic blood donation may be needed.
"Normal" vs. optimal
Lab reference ranges are based on the general population, including people who are obese, sedentary, chronically stressed, and metabolically unhealthy. "Normal" means you fall within the 95th percentile of the population. It does not mean optimal.
A 40-year-old man with a total testosterone of 320 ng/dL, fasting glucose of 104, and vitamin D of 28 ng/mL is technically "normal" by lab standards. He will almost certainly have symptoms. The goal isn't to be normal, it's to be optimized.
How to prepare for your blood draw
- Fast for 8-12 hours, water is fine and encouraged. Avoid food, coffee, and supplements.
- Draw blood in the morning, ideally before 10 AM. Testosterone and cortisol are highest in the morning, and this is the standard for hormone panels.
- Stay hydrated, dehydration concentrates the blood, which can artificially elevate hematocrit and other values. Drink plenty of water the evening before and morning of.
- Avoid intense exercise for 24 hours before the draw, heavy training can transiently affect CRP, cortisol, and muscle enzymes.
- Take your usual medications unless your provider says otherwise.
How often should you test?
- Baseline panel, everyone should have one. If you've never had comprehensive bloodwork, start here.
- Follow-up, every 3-6 months if you're on treatment (TRT, GLP-1s, etc.) or actively optimizing.
- Maintenance, once or twice per year for healthy adults monitoring long-term trends.
The value of bloodwork isn't a single snapshot, it's tracking trends over time. One data point tells you where you are. Multiple data points tell you where you're heading.