Carries oxygen through your body. Low hemoglobin means anemia — fatigue, brain fog, cold hands and feet, shortness of breath. Women are far more commonly affected due to menstruation.

Watch for: fatigue + low hemoglobin together. Do not ignore this combination. Ask for iron, ferritin, and B12 alongside.

Your iron storage protein. This is the one most doctors overlook. You can have a "normal" ferritin of 14 and feel exhausted, losing hair, and struggling to focus — because the normal range is wide. Optimal is closer to 50–100.

Watch for: hair loss, fatigue, brain fog with ferritin under 50. Push for this number specifically, not just "iron levels."

Your immune army. Chronically elevated WBC even within normal range can signal ongoing low-grade inflammation or infection. Low WBC can indicate immune suppression.

Watch for: persistent high-normal WBC alongside fatigue or frequent illness. Worth trending over time.

Involved in clotting. Too low and you bruise and bleed easily. Too high can indicate inflammation or clotting risk. Usually stable but worth knowing your baseline.

Watch for: easy bruising or unexplained bleeding with low platelets. Unusually high platelets warrant follow-up.

Your blood sugar after fasting. The standard cutoff for prediabetes is 100–125. But research shows metabolic dysfunction can begin well before that. A fasting glucose of 95 is technically normal — but worth paying attention to.

Watch for: fasting glucose creeping up year over year even within normal range. This is a trend, not a single number.

A 3-month average of your blood sugar. Far more informative than a single fasting glucose. Shows patterns, not snapshots. Prediabetes starts at 5.7%. Optimal is 4.8–5.3%.

Watch for: anything above 5.4% trending upward. Do not wait for 5.7% to pay attention.

Kidney function markers. eGFR tells you how well your kidneys are filtering. Most people have no symptoms until function has declined significantly — this is exactly why baseline trending matters.

Watch for: eGFR declining year over year even if still above 60. Kidneys are silent until they are not.

Liver stress markers. Elevated levels can indicate fatty liver, alcohol effect, medication stress, or inflammation. Often silent. The optimal range is tighter than standard normal.

Watch for: ALT or AST at the high end of normal alongside weight gain, fatigue, or alcohol use. Worth investigating.

Electrolytes that regulate fluid balance, nerve function, and heart rhythm. Usually stable in healthy adults. Imbalances can come from dehydration, diuretics, poor diet, or kidney issues.

Watch for: low potassium alongside muscle cramps, fatigue, or heart palpitations. More common than people realize.

The master signal that tells your thyroid how hard to work. High TSH means your thyroid is being pushed harder than it should be — often a sign of hypothyroidism. Many women with TSH between 2.5 and 4.0 are told they are normal but feel exhausted, cold, and foggy. The optimal range is narrower for a reason.

Watch for: TSH above 2.5 alongside fatigue, weight gain, hair loss, constipation, or cold intolerance. Ask for Free T3 and Free T4 alongside TSH.

The storage form of thyroid hormone. Your body converts T4 into the active T3. Low Free T4 even with a normal TSH can indicate thyroid insufficiency.

Watch for: low-normal Free T4 combined with symptoms. Conversion problems (T4 to T3) are common and often missed.

The active thyroid hormone. This is what actually gets used by your cells. You can have normal TSH and T4 but low Free T3 and feel every hypothyroid symptom. This is why a full panel matters.

Watch for: Free T3 in the lower half of normal alongside symptoms. This is the number most worth pushing to get tested.

Thyroid peroxidase antibodies. Elevated levels indicate your immune system is attacking your thyroid — the hallmark of Hashimoto's disease, the most common cause of hypothyroidism. Many people have Hashimoto's for years before TSH becomes abnormal.

Watch for: any elevation above normal. Even mildly elevated TPO with normal thyroid hormones warrants monitoring and lifestyle attention.

The primary estrogen. Governs mood, bone density, skin, sleep, libido, and cardiovascular health. Declining estrogen in perimenopause drives many of the symptoms women are told are "just aging." It is not just aging. It is hormones.

Watch for: declining estradiol alongside poor sleep, hot flashes, mood changes, brain fog, or vaginal dryness. Test on day 3 of your cycle for the most meaningful baseline.

The calming counterpart to estrogen. Low progesterone causes anxiety, sleep disruption, heavy periods, and PMS. Declines earlier than estrogen in perimenopause. Often overlooked.

Watch for: anxiety, poor sleep, and irregular cycles with low progesterone. Test on day 21 of a 28-day cycle for the most accurate luteal phase reading.

Not just a male hormone. Women need testosterone for libido, energy, muscle mass, motivation, and bone density. Men with low testosterone experience fatigue, depression, low libido, and loss of muscle. Both sexes are underserved by providers who do not order this routinely.

Watch for: low energy, low libido, difficulty building muscle, and mood changes with testosterone at the lower end of normal for your sex.

Follicle stimulating hormone and luteinizing hormone. As ovarian reserve declines, FSH rises — your brain working harder to stimulate the ovaries. Rising FSH is one of the earliest markers of perimenopause, often years before periods become irregular.

Watch for: FSH above 10 in your 30s or 40s. This is your early warning system for perimenopause and warrants a conversation about hormones sooner rather than later.

A precursor hormone made by your adrenal glands. Declines with age and chronic stress. Low DHEA-S is associated with fatigue, low libido, poor immune function, and accelerated aging. Often a reflection of adrenal health.

Watch for: DHEA-S in the lower quartile of normal alongside chronic fatigue and stress. Trending this over years is more valuable than a single reading.

Not really a vitamin — it is a hormone that influences over 1,000 genes. Critical for immune function, bone density, mood, sleep, and inflammation. The majority of adults are deficient. Normal starts at 20 but research strongly associates levels above 50 with significantly better outcomes.

Watch for: anything under 40 as a reason to supplement. Under 30 is a genuine deficiency. Under 20 is an urgent correction.

Essential for nerve function, red blood cell production, DNA synthesis, and energy. Deficiency causes fatigue, brain fog, tingling in hands and feet, and mood changes. The standard normal starts at 200 — many people feel the effects of deficiency well above that. Optimal is the upper half of the range.

Watch for: B12 under 400 alongside neurological symptoms or fatigue. Vegans, vegetarians, and those on metformin are at highest risk.

Involved in over 300 enzymatic reactions. Critical for sleep, muscle function, blood sugar regulation, anxiety, and heart rhythm. Most standard panels measure serum magnesium — ask for RBC magnesium, which is far more accurate. Deficiency is extremely common due to soil depletion and stress.

Watch for: poor sleep, muscle cramps, anxiety, constipation, or headaches with low-normal RBC magnesium. One of the most impactful supplements to correct.

Essential for immune function, wound healing, hormone production, and skin health. Low zinc is associated with frequent illness, poor wound healing, hair loss, and impaired taste and smell. Often depleted by stress, alcohol, and poor diet.

Watch for: frequent colds, slow healing, or hair loss with zinc in the lower half of normal.

Measures EPA and DHA in your red blood cells. Critical for cardiovascular health, brain function, inflammation, and mood. Most Americans are significantly below optimal. The standard "normal" of 4% is associated with average cardiovascular risk — optimal is 8–12%.

Watch for: omega-3 index under 6% as a strong reason to supplement with high-quality EPA/DHA. This is one of the most impactful labs you can optimize.

Your primary inflammation marker. Chronic low-grade inflammation is at the root of most chronic disease including heart disease, diabetes, Alzheimer's, and cancer. A value under 3 is considered normal. Under 1 is where you want to be.

Watch for: hsCRP above 1.0 as a signal to investigate diet, sleep, stress, gut health, and infection. Do not ignore "normal" inflammation.

A better predictor of cardiovascular risk than LDL cholesterol alone. ApoB counts the actual number of atherogenic particles — the ones that cause plaque. You can have a normal LDL and a high ApoB. This is the test longevity-focused physicians push hardest.

Watch for: ApoB above 90 regardless of LDL. If your doctor only checks LDL, ask specifically for ApoB.

An amino acid that damages blood vessels when elevated. Associated with cardiovascular disease, cognitive decline, and stroke risk. Elevated homocysteine is often driven by B12, B6, or folate deficiency and is highly correctable with supplementation.

Watch for: homocysteine above 10. Highly actionable — often correctable with methylated B vitamins.

One of the most important and least ordered markers. Insulin resistance develops years before blood sugar becomes abnormal. High fasting insulin with normal glucose means your body is working hard to keep sugar in check — a warning sign most standard panels miss entirely.

Watch for: fasting insulin above 10 even with normal glucose. This is metabolic dysfunction in early stages. Highly responsive to diet and lifestyle changes.

Your primary stress hormone. Should be highest in the morning and decline through the day. Chronically elevated cortisol drives belly fat, poor sleep, immune suppression, and hormonal disruption. Chronically low cortisol causes exhaustion that no amount of sleep fixes. Test in the morning, fasted, before 9am.

Watch for: cortisol at either extreme. High AM cortisol with poor sleep and anxiety. Low AM cortisol with profound fatigue and inability to handle stress.