These lab tests screen for optimal health

(Because the scale and the mirror are telling you less than you think)

Quick note before we dive in: I’m a certified personal trainer and health coach — not a doctor. Nothing in this post should be taken as medical advice. These are biomarkers I’ve studied, follow personally, and find valuable in the context of overall health — but what’s right for you depends on your individual health history, genetics, age, symptoms, and a whole lot more. Please bring these to your doctor, share your concerns, and let them guide you on what makes sense for your specific situation. The goal here is to start a conversation — not replace one.

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A special thank-you to two people who helped shape this post. Melissa Hoegg, a nurse practitioner specializing in hematology, offered invaluable clinical perspective on iron testing, B12, and practical considerations around ordering labs. And a client who is a heart surgeon recommended adding the coronary artery calcium score — a test she considers one of the most underutilized tools in cardiovascular prevention. I’m grateful for both of their expertise.

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I want to ask you something honest. When was the last time you actually looked inside your body?

Not in the mirror. Inside. At the systems running quietly in the background — the ones that might tell you something important about where your health is heading long before any obvious symptoms show up.

We’ve been sold a version of health that lives almost entirely on the surface. The number on the scale. The size of our jeans. The way we look in photos. And while none of those things are meaningless, they’re an incomplete picture of what’s actually happening inside the body.

In my years of working with clients, I’ve seen people who looked fit and felt fine — and had bloodwork that told a very different story. And I’ve seen the reverse. Appearance and internal health are not always the same thing.

This post covers some of the biomarkers I find most interesting and potentially valuable — what they measure, what the general ranges seem to suggest, and the lifestyle habits research associates with improvement. Take it to your next appointment. Ask questions. Find a provider who partners with you.

“For the Lord sees not as man sees: man looks on the outward appearance, but the Lord looks on the heart.” — 1 Samuel 16:7

God has always been more interested in what’s underneath than what’s visible on the surface. Our approach to health is worth reflecting that too.

A practical note from Melissa Hoegg, NP: Two real-world considerations worth knowing before you bring this list to your doctor. First, insurance may not cover many of these labs depending on how they’re coded — it’s worth asking upfront what’s covered under your plan. Second, ordering providers are responsible for following up on results, so some providers may be hesitant to order tests they’re less familiar with or don’t routinely manage. Going in with questions rather than demands, and being open to their guidance, tends to go further.

1. Ferritin & Full Iron Panel

Recommended as a top priority by Melissa Hoegg, NP, hematology specialist

What it measures

Ferritin measures your stored iron — the reserves your body draws on when circulating iron is insufficient. It’s the most sensitive marker for iron deficiency, and it’s critically important to look at it alongside a full iron panel (serum iron, TIBC, and transferrin saturation) for proper interpretation, since ferritin alone can be elevated by inflammation even when iron stores are actually low.

Iron deficiency is one of the most common and most missed nutritional deficiencies — particularly in women. It frequently presents as fatigue, poor exercise recovery, brain fog, cold intolerance, restless legs, and hair loss. Many women are told their iron is “fine” when only hemoglobin is checked and ferritin is never tested at all.

Melissa’s clinical note: “We do a lot of iron management where I work. Checking a ferritin is essential, along with a full iron panel for proper interpretation. It’s extremely important to monitor in teenage girls through menopause, especially during pregnancy and postpartum. It’s also important for men as a screening tool for iron overload, which if missed can cause cirrhosis. And if ferritin is low in a man or non-menstruating woman, it can be the first sign of colon cancer. I’d recommend a yearly check for everyone.”

General reference ranges

Iron deficiency (clinical threshold): Below 30 μg/L in adults

Early iron deficiency may begin: Below 50 μg/L in some research

Optimal range (women): 50–150 μg/L is often considered a functional target

Risk of iron overload (menstruating women): Above 150 μg/L

Risk of iron overload (men and non-menstruating women): Above 200 μg/L

An important caveat: ferritin is an acute phase reactant, meaning it rises with inflammation even when iron stores are low. This is why a full iron panel matters — ferritin alone can be misleading in the context of chronic inflammation or illness. If your ferritin is elevated, it doesn’t automatically mean your iron stores are fine. Your doctor will interpret it alongside the full picture.

Also worth knowing: many standard lab reference ranges for ferritin are set far too low — particularly for women. A ferritin of 12 or 15 ng/mL may technically be within the “normal” range at some labs, but growing research suggests this threshold misses a large number of people with clinically significant iron deficiency.

Lifestyle and treatment considerations

• Iron-rich foods include red meat, organ meats, shellfish, dark leafy greens, lentils, beans, and pumpkin seeds

• Vitamin C consumed alongside plant-based iron sources significantly improves absorption

• Calcium and coffee/tea can inhibit iron absorption — spacing these apart from iron-rich meals may help

• If deficiency is confirmed, oral or IV iron supplementation under medical supervision is the most effective intervention

• For men or non-menstruating women with low ferritin — bring this to your doctor promptly, as it warrants investigation into the cause

2. Vitamin D (25-OH Vitamin D)

Flagged by Melissa Hoegg, NP as one of the most frequently abnormal tests in clinical practice

What it measures

Vitamin D functions more like a hormone than a traditional vitamin and is involved in a wide range of biological processes — immune function, bone health, mood, muscle function, hormonal balance, and more. The test to ask for is 25-hydroxyvitamin D (25-OH Vitamin D), which captures both sun exposure and dietary intake.

Deficiency is staggeringly common — estimated to affect 40% or more of American adults — often without obvious symptoms beyond vague fatigue, low mood, or getting sick frequently. For women, Vitamin D is particularly relevant to bone density, hormonal health, and immune regulation.

General reference ranges

Deficient: Below 20 ng/mL

Insufficient: 20–29 ng/mL

Sufficient by conventional standards: 30–60 ng/mL

Often targeted as optimal: 40–60 ng/mL by many functional medicine practitioners

There is ongoing scientific discussion about where the optimal level falls. Your doctor can help interpret your specific result and whether supplementation makes sense for you.

Lifestyle habits associated with improvement

• Sunlight exposure — 10–20 minutes of midday sun on exposed skin several times a week, though this varies by skin tone, season, and latitude

• Dietary sources include fatty fish, egg yolks, and fortified foods — but food alone rarely corrects meaningful deficiency

• Vitamin D3 supplementation is the most reliable correction approach — doses vary based on baseline. D3 taken with K2 is often recommended

• Magnesium is required for Vitamin D metabolism — low magnesium can limit how effectively you use Vitamin D

• Test your levels before supplementing and retest after 3 months to track your response

3. Vitamin B12, Folate & Methylmalonic Acid (MMA)

Recommended by Melissa Hoegg, NP as part of a complete picture when homocysteine is elevated

What it measures

Vitamin B12 is essential for nerve function, DNA synthesis, red blood cell production, and neurological health. Deficiency can cause irreversible nerve damage if left unaddressed long enough — and it often develops silently, since symptoms can be vague and gradual. Folate works alongside B12 in many of the same processes.

Here’s the important clinical nuance: serum B12 alone can look normal even when a functional deficiency exists at the cellular level. This is why Melissa and other hematology specialists recommend pairing B12 testing with methylmalonic acid (MMA) and homocysteine when deficiency is suspected. MMA is a more sensitive functional marker — it rises when B12 is functionally insufficient at the cellular level, even when serum B12 appears normal.

Melissa’s clinical note: “We always make sure to check for B12, folate, and methylmalonic acid (MMA) together when we’re investigating homocysteine or anemia. MMA is particularly useful because it confirms whether B12 is actually being used properly at the cellular level, not just whether it’s present in the blood.”

B12 deficiency is particularly common in people over 50 (due to decreased stomach acid needed for absorption), those taking metformin for diabetes, vegans and vegetarians, people with Crohn’s disease or other GI absorption issues, and those with a history of bariatric surgery.

General reference ranges

B12 — conventional normal: 200–900 pg/mL, though many clinicians consider below 400 worth watching

Folate — deficiency: Below 3–4 ng/mL

MMA — elevated (suggests functional B12 deficiency): Above 0.4 μmol/L

Lifestyle and treatment considerations

• B12 is found almost exclusively in animal products — meat, fish, eggs, dairy. Vegans and vegetarians should supplement

• Methylcobalamin is generally considered the more bioavailable form of B12 supplementation

• If absorption is the issue (common in older adults and those on metformin), sublingual or injectable B12 may be more effective than oral

• Folate is found in leafy greens, legumes, and fortified foods. Most prenatal vitamins contain adequate folate

• If MMA is elevated, work with your doctor to determine the right supplementation approach and dosing

4. HbA1c (Hemoglobin A1c)

What it measures

HbA1c reflects your average blood sugar level over roughly the past two to three months. When glucose circulates in your bloodstream, it attaches to hemoglobin in your red blood cells. Since red blood cells live about 90 days, this test gives a longer window into blood sugar patterns than a single fasting glucose reading.

General reference ranges

Often considered optimal: Below 5.4%

Worth watching: 5.4–5.6%

Prediabetes range: 5.7–6.4%

Type 2 diabetes range: 6.5% or higher

Something worth knowing: the “normal” range on a standard lab report often goes up to 5.7%. Some research suggests that metabolic risk may begin rising earlier. Your doctor can help interpret what your specific number means in your full health picture.

Lifestyle habits associated with improvement

• Reducing refined carbohydrates and added sugars

• Including protein and fiber at meals to slow glucose absorption

• Resistance training — muscle helps the body manage blood sugar more efficiently

• Managing chronic stress — cortisol can raise blood sugar directly

• Prioritizing quality sleep — even short-term sleep deprivation affects glucose metabolism

5. Fasting Insulin

What it measures

Fasting insulin measures how much insulin your pancreas is producing after an overnight fast. When cells become resistant to insulin, the pancreas compensates by producing more — and this can go on for years before blood sugar itself rises. Fasting insulin can therefore signal a developing problem that HbA1c and fasting glucose haven’t yet reflected.

This is not part of most routine panels. You may need to ask for it specifically.

General reference ranges

Often considered optimal: Below 8 μIU/mL

Worth discussing with your doctor: 8–12 μIU/mL

May suggest insulin resistance: Above 12 μIU/mL

Lifestyle habits associated with improvement

• Reducing ultra-processed foods and refined carbohydrates

• Pairing carbohydrates with protein, fiber, and healthy fat to stabilize blood sugar

• Resistance training — muscle tissue plays a key role in insulin sensitivity

• Adequate sleep — sleep deprivation reduces insulin sensitivity measurably

• Stress management — chronic cortisol elevation promotes insulin resistance

6. HOMA-IR (Insulin Resistance Score)

What it measures

HOMA-IR is a calculated score derived from fasting insulin and fasting glucose: (fasting insulin x fasting glucose) ÷ 405. It’s not a separate blood draw — it uses the two values above. The combination can detect insulin resistance that neither number reveals alone, potentially 10–20 years before a diabetes diagnosis.

It’s used more in research and functional medicine than in conventional practice, but it’s worth knowing about and discussing with your doctor if you’re concerned about metabolic health.

General reference ranges

Often considered optimal: Below 1.0

Mild concerns: 1.0–2.0

Moderate concerns: 2.0–3.0

Significant insulin resistance suggested: Above 3.0

Lifestyle habits associated with improvement

The same habits that improve fasting insulin and HbA1c improve HOMA-IR — resistance training, dietary changes that support blood sugar stability, quality sleep, and stress management. Some people see meaningful changes within a few months of consistent lifestyle adjustments.

7. hs-CRP (High-Sensitivity C-Reactive Protein)

What it measures

hs-CRP is a marker of systemic inflammation produced by the liver. Chronic low-grade inflammation is considered a significant underlying factor in cardiovascular disease, type 2 diabetes, and other chronic conditions — often without obvious symptoms in its early stages.

hs-CRP is not specific — it can be elevated for many reasons including illness, injury, and autoimmune conditions. If elevated, your doctor will want to identify the underlying cause.

General reference ranges

Often considered optimal: Below 0.5 mg/L

Low risk: Below 1.0 mg/L

Moderate risk: 1.0–3.0 mg/L

High risk: Above 3.0 mg/L

Test when you’re well — active illness or injury will temporarily elevate hs-CRP and won’t reflect your true baseline.

Lifestyle habits associated with improvement

• An anti-inflammatory diet — vegetables, fruits, whole grains, fatty fish, olive oil, nuts; reducing ultra-processed foods

• Regular exercise — consistent moderate-intensity movement is associated with lower systemic inflammation

• Quality sleep and stress management — both directly affect inflammatory markers

• Omega-3 fatty acids from fish and quality fish oil have meaningful research support

• Address dental/gum health — a surprisingly common and overlooked driver of elevated hs-CRP

8. Triglycerides

What it measures

Triglycerides are the form of fat your body uses to store and transport energy. When you consume more calories than the body immediately needs — particularly from refined carbohydrates and sugar — the liver packages the excess into triglyceride-rich particles. They’re directly responsive to dietary patterns and can change meaningfully within weeks of lifestyle adjustments.

General reference ranges

Often considered optimal: Below 100 mg/dL

Acceptable: 100–149 mg/dL

Borderline high: 150–199 mg/dL

High: 200 mg/dL and above

Lifestyle habits associated with improvement

• Reducing refined carbohydrates and added sugar — primary dietary drivers

• Reducing alcohol — the liver converts it directly to triglycerides

• Increasing omega-3 fatty acids through fatty fish or quality fish oil

• Regular aerobic exercise and resistance training

9. HDL Cholesterol

What it measures

HDL particles help transport excess cholesterol from arteries back to the liver for removal. Higher HDL is generally considered protective. Low HDL frequently travels alongside high triglycerides — and when that combination is present, insulin resistance is often an underlying factor.

General reference ranges (women)

Often considered optimal: Above 60 mg/dL. Above 70 mg/dL even more favorable

Acceptable: 50–59 mg/dL

Low — worth discussing: Below 50 mg/dL

Lifestyle habits associated with improvement

• Exercise — particularly aerobic activity — is one of the most consistent tools for raising HDL

• Healthy fats from olive oil, avocado, nuts, and fatty fish

• Reducing refined carbohydrates, which research associates with suppressed HDL

• Maintaining a healthy body weight, particularly reducing excess visceral fat

10. ApoB (Apolipoprotein B — Particle Count)

What it measures

Standard cholesterol panels measure LDL cholesterol — the weight of cholesterol in LDL particles. ApoB counts the actual number of atherogenic particles in your blood (LDL, VLDL, IDL), because there is exactly one ApoB protein per particle. Some researchers argue particle count — not cholesterol weight — is what drives plaque development.

Think of it this way: ten small cars and one large truck might carry the same total weight, but ten cars make ten separate trips through traffic. More trips means more chances for something to go wrong.

ApoB is not yet part of most standard panels but is increasingly recommended by leading cardiologists as a more informative lipid marker. Worth asking about.

General reference ranges

Often considered optimal: Below 70 mg/dL for most adults

Acceptable: 70–90 mg/dL

Worth discussing with your doctor: 90–130 mg/dL

High risk range: Above 130 mg/dL

Lifestyle habits associated with improvement

• Reducing saturated fat and replacing with unsaturated fat sources

• Increasing soluble fiber — oats, beans, lentils, apples, psyllium

• A diet rich in vegetables, legumes, and whole grains

• Regular exercise, particularly resistance training

• Improving insulin resistance — metabolic dysfunction increases particle production

• For some people, lifestyle changes alone may not be sufficient — medication is very effective and worth discussing with your doctor

11. Coronary Artery Calcium Score (CAC)

Recommended by a current client, a heart surgeon, as one of the most underutilized tools in cardiovascular prevention

What it measures

The CAC score is a non-invasive CT scan of the heart that measures the amount of calcified plaque in the coronary arteries. Calcified plaque is a direct marker of atherosclerosis — the buildup of plaques in artery walls that causes heart disease. Unlike blood tests, which measure risk factors and biomarkers, the CAC score shows what’s actually happening in the arteries themselves.

This is not a blood test — it’s an imaging study. It uses about the same radiation as a mammogram. It’s particularly valuable for people in the intermediate risk range who are uncertain about whether to start statin therapy, as a score of zero is one of the strongest negative predictors of cardiovascular events available.

One research finding worth noting: people who learn their CAC score tend to be more motivated to make lifestyle changes and adhere to treatment. Seeing actual plaque in your arteries — or the absence of it — is a compelling reality check in a way that a number on a lab report sometimes isn’t.

How scores are interpreted

0: No plaque detected. Associated with very low near-term cardiovascular risk. Sometimes called the ‘power of zero’

1–99: Mild plaque present. Low to moderate risk. Lifestyle changes typically recommended

100–399: Moderate plaque. Moderate to high risk. Most guidelines recommend discussing statin therapy at this level

400 and above: Extensive plaque. High risk. Statin therapy strongly recommended alongside lifestyle intervention

A CAC score of 0 is considered the strongest available negative risk marker for cardiovascular disease — stronger than cholesterol screening or most other risk factors alone. However, a score of 0 doesn’t mean zero risk forever, and it doesn’t replace healthy lifestyle habits.

CAC scoring is generally recommended for adults aged 40 and above who are at intermediate cardiovascular risk or who want more information to guide decisions about statin therapy. It’s typically not covered by insurance, but it’s often available for $75–$150 out of pocket at imaging centers. Ask your doctor if it might be appropriate for you.

Lifestyle habits associated with better outcomes

• All the cardiovascular lifestyle habits we’ve discussed — reducing ApoB, lowering hs-CRP, improving insulin sensitivity — also slow plaque progression

• A CAC score doesn’t change with lifestyle interventions in the short term, but the progression rate can be slowed

• If your score is elevated, your doctor may recommend medication alongside lifestyle change — statins have shown evidence for slowing plaque progression

Additional Tests Worth Knowing About for Longevity

Beyond the eleven markers above, here are some additional biomarkers worth learning about from a long-term health perspective. Not all are routinely ordered, and not all will be right for everyone. Think of this as a starting point for conversation with your healthcare provider.

Lp(a) — Lipoprotein little a

Lp(a) is a genetically determined cholesterol particle not included in a standard lipid panel. An estimated 20% of people have elevated levels, and most have no idea. It’s an independent cardiovascular risk factor and doesn’t respond significantly to lifestyle changes — but knowing your number informs your overall risk picture. Most researchers suggest testing it once in a lifetime.

Homocysteine

An amino acid that when elevated has been associated in research with increased cardiovascular risk, cognitive decline, and stroke. Rarely included in routine panels but inexpensive to test. It responds well to B vitamins — particularly B6, B12, and folate — and connects directly to the B12/MMA testing discussed earlier.

Full Thyroid Panel (TSH, Free T3, Free T4)

Many standard physicals only check TSH as a screening tool. But TSH alone can miss a more complete picture of thyroid function. Free T3 is the active thyroid hormone and, alongside Free T4, gives a more thorough look at how your thyroid is actually functioning. Thyroid dysfunction is common in women and frequently underdiagnosed.

Liver Enzymes (ALT and AST)

Non-alcoholic fatty liver disease is now one of the most common liver conditions in the world, and most people who have it don’t know. Early elevation in ALT and AST can be one of the first signals. When caught early, fatty liver is typically very responsive to lifestyle changes.

Kidney Function (eGFR and Creatinine)

Your kidneys filter your blood continuously and kidney disease is frequently silent until advanced.

Melissa’s clinical note: “Thank you for putting eGFR on here. Interesting thing — it never ‘flags’ abnormal yet is often the first indicator of kidney disease. Many busy PCPs never notice a decrease or discuss it with their patients. It’s worth asking your doctor to walk you through this number specifically at your next visit.”

DHEA-S

A hormone produced by the adrenal glands that declines with age. Considered by some researchers to be a useful marker of biological aging and adrenal health. Low DHEA-S is associated with fatigue, reduced stress resilience, and poor recovery. Not a routine test but worth asking about, particularly in perimenopause and postmenopause.

Testosterone (Total and Free) for Women

Plays a meaningful role in energy, mood, muscle building, libido, and cognitive function in women. Declines with age, particularly after menopause. Worth asking about — especially if you’re experiencing unexplained fatigue, difficulty building muscle, or mood changes.

Complete Blood Count (CBC)

Gives a broad picture of red blood cells, white blood cells, and platelets. Can flag anemia, immune system abnormalities, and early warning signs across multiple systems. Often included in a routine panel — but worth reviewing with your doctor rather than ignoring if numbers are out of range.

Epigenetic Age Testing

On the cutting edge and not yet mainstream. DNA methylation tests like GrimAge estimate your biological age — how old your cells are behaving — as opposed to your chronological age. Companies like TruDiagnostic offer direct-to-consumer testing. The research is still developing but may eventually become one of the most direct ways to measure how lifestyle choices are affecting how you’re aging at the cellular level.

A note before you take any of this to your doctor

I want to be clear: I’m not a doctor, and nothing in this post is medical advice. These are biomarkers I’ve studied, find genuinely interesting, and believe are worth being aware of. But what matters for you specifically — which tests make sense, what your numbers mean, and what to do about them — is deeply personal.

Health is individual. Your care plan should be shaped by your health history, genetics, current symptoms, age, family history, environment, occupation, and a whole range of factors that only a healthcare provider who knows you can fully weigh. A test that’s appropriate for one person may be unnecessary or even misleading for another.

Bring this list to your next appointment. Share what you’ve been learning. Ask which of these might be worth testing in your situation and why.

Find a provider who takes your curiosity seriously and partners with you in understanding your body — not just treating symptoms after the fact.

The goal of knowing your numbers isn’t anxiety. It’s awareness. It’s the kind of stewardship that says: I want to understand what’s happening inside the body God gave me so I can take care of it wisely.

True health isn’t just what you look like. It’s what your body is doing at the cellular level — how well your blood sugar is regulated, how inflamed your arteries are, how efficiently your cells respond to insulin, how protected your cardiovascular system is. The mirror tells you almost none of that.

The good news is that almost every marker on this list responds to the same foundational lifestyle habits: consistent resistance training, adequate protein and fiber, reducing ultra-processed foods, quality sleep, and stress management. One solid foundation tends to move multiple numbers in the right direction simultaneously.

Steward your body well. Ask good questions. And find a doctor who will help you get real answers.

If you want to build the lifestyle foundation that supports these biomarkers — through the lens of faith, science, and sustainable habit — the 6:19 Method June cohort is opening soon. Join the waitlist at dg-fit.com/619method.