Feeling “low energy” isn’t one thing. It’s a system story. Hormones cue your cells to make ATP, shift fuel between glucose and fat, deliver oxygen, and clear the exhaust. When that choreography is off, you feel it. Labs turn that invisible ballet into a dashboard you can read. But the right biomarkers matter, and timing and context matter just as much as the numbers. Ready to learn which tests actually map to how energized you feel?
Energy, by Design: How Hormones Drive Power
Energy starts with fuel delivery and mitochondrial output. Insulin gets glucose into cells. Thyroid sets the metabolic gear. Cortisol sets the day-night rhythm and mobilizes fuel under stress. Sex hormones shape muscle, mood, and sleep architecture. Iron moves oxygen to the mitochondria so the last step of ATP production can run at full tilt. When any of these are off, energy drops, sometimes subtly, sometimes spectacularly.
So the smartest biomarker panel isn’t random. It follows the mechanism from signal to substrate to output. Want to see what that looks like in practice?
Thyroid: Your Metabolic Thermostat
Thyroid hormones set baseline energy expenditure. They influence heart rate, heat production, gut motility, and how fast cells turn nutrients into ATP. The American Thyroid Association considers TSH the front door, with free hormones providing context. Think of TSH as your thermostat setting and free T4/T3 as the actual air temperature in the room.
TSH (thyroid-stimulating hormone)
TSH rises when the pituitary senses not enough thyroid hormone and falls when there’s plenty. It’s sensitive to small changes. It also drifts with illness, pregnancy, and certain meds, so interpret in context.
Free T4 and Free T3
Free T4 is the main circulating prohormone; free T3 is the active driver at the cellular level. Low free T4 with a high TSH fits primary hypothyroidism. Normal T4 with symptoms may push you to look at conversion, illness, or meds that block deiodinase activity.
Thyroid peroxidase antibody and thyroglobulin antibody
These antibodies flag autoimmune thyroiditis, the most common cause of underactive thyroid in iodine-sufficient regions. Antibodies don’t predict the exact pace of change but help explain a fluctuating course and guide monitoring.
Reverse T3 (rT3)
rT3 is an inactive isomer formed during illness or caloric deficit. It can rise when the body conserves energy. It’s more of a physiology clue than a primary decision-maker in guidelines, so treat it as a context marker, not a diagnosis in itself.
Because thyroid interacts with everything from lipids to periods to pregnancy, timing and life stage matter. Curious where the stress system plugs in?
Cortisol and DHEA: Rhythm, Stress, and Stamina
Cortisol should peak in the morning, drop through the day, and be low at night. That curve supports alert mornings and restful sleep. Chronic flattening can feel like wired-tired days and restless nights. Endocrine Society guidance uses specific tests to evaluate true disorders like Cushing’s or adrenal insufficiency, but patterning still matters for energy.
8 a.m. serum cortisol
Morning cortisol screens for deficiency when interpreted alongside symptoms and, if needed, an ACTH stimulation test. Low values with weakness, weight loss, and low blood pressure raise concern for adrenal insufficiency.
Diurnal salivary cortisol (multiple samples)
Noninvasive sampling across the day maps the curve. Helpful for circadian alignment questions and sleep complaints. Assays vary, so use the same lab for repeats.
24-hour urinary free cortisol
Captures integrated cortisol production over a day. It’s a go-to for suspected cortisol excess when collected correctly.
ACTH and DHEA-S
ACTH helps localize cortisol problems to pituitary or adrenal. DHEA-S, a stable adrenal androgen, trends with adrenal output and aging. It’s not a sole energy marker but adds texture to the stress-and-recovery picture.
“Adrenal fatigue” isn’t a recognized diagnosis, but real conditions like insufficiency or excess are. Sleep, shift work, and heavy training can blunt or shift the curve, too. Want to see how your fuel system influences the day-to-day energy swings?
Insulin, Glucose, and Metabolic Flexibility
Stable energy depends on how smoothly you switch between glucose and fat. If insulin stays high, fat burning stalls and post-meal crashes become a pattern. If insulin is too low or delayed, you can feel jittery, then drained. Large studies link insulin resistance with fatigue and brain fog, not just diabetes risk.
Fasting glucose
A quick look at baseline glycemia. It misses early insulin resistance, so pair it with insulin when possible.
Fasting insulin
Elevated fasting insulin suggests the pancreas is working harder to keep glucose normal. Over time, that extra push feels like heaviness after meals and difficulty with steady energy.
HbA1c
Three-month average of blood sugar exposure. Great for trend-watching, but conditions like anemia can skew it. If the story and the number disagree, dig deeper.
Oral glucose tolerance test with insulin
Shows how quickly glucose rises and how insulin responds. Early spikes with delayed insulin can explain the “2 p.m. wall.” Athletes may show brisker clearance, a marker of metabolic flexibility.
C-peptide
Tracks your own insulin production. Useful when distinguishing low insulin production from high insulin resistance.
Fun reality check: even a 10-minute walk after a carb-heavy meal shuttles glucose into muscle without insulin by activating GLUT4. That’s why movement steadies energy so quickly. But what if the issue isn’t fuel, it’s oxygen delivery?
Iron, Blood, and Oxygen Delivery
Hemoglobin carries oxygen. Iron stocks refill hemoglobin. Low supply means tissues run on a partial tank. The result is classic: fatigue, dyspnea on stairs, brain fog. On the flip side, too much iron can drive oxidative stress. Both ends sap energy, just differently.
Complete blood count (CBC)
Hemoglobin and hematocrit show oxygen-carrying capacity. Mean corpuscular volume (MCV) points to microcytic (often iron), macrocytic (often B12/folate), or mixed patterns. Reticulocyte count shows whether the marrow is responding.
Ferritin
Ferritin reflects iron stores. It rises with inflammation, so a normal or high ferritin doesn’t rule out deficiency if C-reactive protein is up. In menstruating individuals, suboptimal ferritin can precede anemia by months, which is why symptoms often arrive before the CBC shifts.
Serum iron, TIBC, and transferrin saturation
These fill in transport and availability. Low transferrin saturation with low ferritin supports iron deficiency; high saturation may suggest overload. If overload is persistent, clinicians sometimes evaluate for hereditary hemochromatosis.
When context matters
Heavy periods, endurance training, frequent blood donation, and GI malabsorption all change the iron math. In pregnancy, needs rise sharply. If iron is off, ask why, not just how much.
Oxygen delivered, check. What about the vitamins that let mitochondria run the Krebs cycle cleanly?
B12, Folate, and Key Cofactors
B12 and folate are required for red blood cell formation and mitochondrial enzymes. Low levels can cause anemia and also neurological symptoms long before blood counts change. The fix isn’t one-size-fits-all; absorption and medications play a role.
Vitamin B12
Serum B12 is a starting point. It can look “normal” while tissue levels are low, especially in older adults or with metformin and acid-suppressing drugs in the mix.
Methylmalonic acid (MMA)
MMA rises when B12-dependent enzymes stall, making it a more specific functional marker. Elevated MMA with low-normal B12 points toward true deficiency.
Folate
Essential for DNA synthesis and red blood cell production. It drops with poor intake and certain meds. Red cell folate reflects longer-term status, though it’s not always necessary.
Homocysteine
Goes up when either B12 or folate pathways are stressed. It’s a helpful tie-breaker when the picture is murky.
Mineral and micronutrient context matters too. Iodine and selenium support thyroid hormone production and activation, though population-level measures like urinary iodine are better for groups than for individuals. Want to see how reproductive hormones shape energy patterns across the month and across decades?
Sex Hormones: Muscle, Mood, and Momentum
Sex hormones don’t just influence fertility. They shape muscle mass, sleep quality, temperature regulation, and brain energy use. That’s why changes at perimenopause or with low testosterone are often felt first as stamina and drive shifts.
Total and free testosterone with SHBG
Total testosterone shows supply; free testosterone shows what’s bioavailable after binding to sex hormone–binding globulin (SHBG). High SHBG, as seen with some oral estrogens or liver conditions, lowers free levels even when total looks fine.
Estradiol and progesterone (timed)
Estradiol rises before ovulation; progesterone peaks mid-luteal. Timing blood draws to cycle day sharpens interpretation. In perimenopause, variability is the rule, which explains why energy and sleep can swing week to week.
LH and FSH
Higher levels with low estradiol support ovarian insufficiency or menopause. In PCOS, LH can be disproportionately elevated relative to FSH, part of a broader metabolic story.
Prolactin
Elevated prolactin can disrupt gonadal hormones, sleep, and mood. Certain meds and stress spur transient bumps, so repeat testing in a calm, fasting morning can be clarifying.
Hormones don’t work in a vacuum. Low-grade inflammation can gum up the works. Which signals tell you recovery is lagging?
Inflammation, Recovery, and Mitochondrial Drag
When inflammatory cytokines rise, mitochondria throttle down and you feel it: less oomph, more effort. Post-viral recovery is a common example. Good news: a few simple labs track the background noise without overcomplicating the picture.
High-sensitivity C-reactive protein (hs-CRP)
Reflects systemic inflammation at low levels. It moves with weight change, sleep debt, infection, and training load. Persistent elevation nudges you to look for sources, from gum disease to sleep apnea.
Erythrocyte sedimentation rate (ESR)
Less specific and slower to change, but if ESR and CRP both run high, chronic inflammation is more likely.
Creatine kinase (CK) when appropriate
CK spikes with intense exercise or muscle injury. Chronically high levels alongside fatigue can signal under-recovered muscle, explaining why power fades late in the week.
Inflammation can also distort other markers, like ferritin and thyroid tests during acute illness. How about the clock that sets the tempo for all of this?
Sleep and Circadian Signals
Your energy depends on when, not just what. The circadian system gates hormone release, body temperature, and mitochondrial efficiency. Shift work, travel, and late-night screens all tug at that timing.
Dim light melatonin onset (DLMO)
Measured in research settings with serial salivary samples, DLMO pinpoints your internal night. Consumer melatonin tests vary in quality, so treat results cautiously. If your rhythm is delayed, even perfect labs can coexist with sluggish mornings.
Morning-evening body temperature and heart rate trends
Not lab tests, but simple metrics that mirror circadian phase and recovery. When the curve is flattened, energy usually is too.
Synchronization matters. If the rhythm is off, you feel off. But hormones also need clean processing and clearance. Where do the liver and kidneys fit?
Liver, Kidneys, and Hormone Handling
Hormones are made, bound, activated, deactivated, and excreted. The liver manages binding proteins and metabolizes hormones; the kidneys excrete byproducts. Subtle slowdowns can nudge levels without classic symptoms.
ALT, AST, and GGT
Liver enzymes hint at metabolic stress from alcohol, fatty liver, or medications. GGT correlates with oxidative stress in population studies and can move with lifestyle changes.
Albumin and bilirubin
Albumin reflects synthetic capacity and affects protein-bound hormones. Bilirubin offers another angle on liver function and red cell turnover.
Creatinine and eGFR
Kidney filtration rate shapes hormone metabolite clearance. In advanced kidney disease, many hormones drift upward due to slower excretion.
One more layer can make or break interpretation: the assay itself. What can trip you up if you’re not looking?
Assay Caveats That Protect You From Misreads
Timing and posture
TSH varies across the day. Cortisol is diurnal. Catecholamines shift with posture. Draw at standard times, ideally fasting morning, unless a test specifies otherwise.
Biotin and supplements
High-dose biotin can distort many immunoassays, especially thyroid and troponin. Most labs recommend pausing biotin for at least a day before testing, longer for mega-doses.
Heterophile antibodies and interference
Rare antibodies can falsely elevate or depress hormone results. If a number makes no biological sense, ask the lab about alternative methods or blocking reagents.
Medications and life stage
Oral estrogens raise SHBG, lowering free testosterone. Glucocorticoids suppress the HPA axis. Pregnancy rewrites thyroid and iron interpretation. Menopause changes the set points. Always interpret through the life-stage lens.
So how do you put this into a coherent, efficient plan without overtesting?
A Simple, Science-Backed Testing Roadmap
Start with the highest-yield signals, then layer in targeted tests based on the story. This is how clinicians align with endocrine and primary care guidelines while actually answering the “Why am I tired?” question.
Core metabolic and recovery set
Basic metabolic panel, CBC, hs-CRP. This trio surfaces anemia, electrolyte issues, kidney function, and background inflammation that can mute energy.
Thyroid core
TSH with reflex to free T4. Add free T3 and thyroid antibodies when symptoms and TSH diverge, or when autoimmune disease is in the differential.
Glucose-insulin status
Fasting glucose and insulin with HbA1c. If energy crashes track meals, consider a structured glucose tolerance test with insulin to map the curve.
Iron availability
CBC, ferritin, transferrin saturation. If low, look for source and stage of deficiency before deciding how to replete.
Stress rhythm
8 a.m. cortisol if deficiency is suspected, or diurnal salivary cortisol to visualize the curve when sleep and alertness are out of sync.
Sex hormone context
Total and free testosterone with SHBG in people with symptoms of low libido, low muscle mass, or low morning energy. Estradiol and progesterone timed to cycle in those with cyclic energy swings or perimenopausal change. LH/FSH for menopausal staging.
Micronutrient checks
B12 with MMA when neuropathy, cognitive fog, or macrocytosis appear. Folate if diet or meds suggest risk.
From there, add specialized tests only when the first wave points somewhere specific. Less scatter, more signal. Want the take-home that keeps you grounded the next time you’re scanning a lab portal?
Putting It All Together
Energy is the sum of signals that deliver fuel, set tempo, carry oxygen, and clear byproducts. The best biomarkers trace that path end to end without chasing noise. Thyroid sets the gear. Cortisol shapes the curve. Insulin and glucose set the fuel mix. Blood and iron deliver oxygen. B12 and folate keep the machinery crisp. Sex hormones fine-tune muscle and sleep. Liver and kidneys handle the cleanup. Inflammation can dim the whole stage.
Lab results are powerful, but they’re not prescriptions. They are clues to be interpreted alongside how you sleep, what and when you eat, how you train, your cycle or life stage, and the medications and supplements you use. Use them to ask better questions, track real change, and build an energy system that fits your life. What piece of your energy story do you want to illuminate first?
Join Superpower today to access advanced biomarker testing with over 100 lab tests.
