FixFirst / Guides
Your lab results, decoded. What the numbers mean, what standard panels miss, and what to do first. Or skip the reading and analyze your own report directly. For commentary on new biomarker research as it breaks, see FixFirst Research.
Free tools
Quick, evidence-based calculators that show the formula and how the result varies for you. Computed in your browser — nothing is sent anywhere.
eGFR Calculator (CKD-EPI 2021)
Estimate kidney function from creatinine, age and sex using the 2021 race-free CKD-EPI equation, with a toggle for the Japanese (JSN) equation and your CKD stage explained.
LDL Cholesterol Calculator
Estimate LDL from total cholesterol, HDL and triglycerides using the Friedewald and Sampson (NIH) equations, in mg/dL or mmol/L, with how optimal targets vary by guideline.
Symptom investigation
For when the tests say fine but you don't feel it, and for finding the tests your standard panel routinely skips.
Labs Normal, Still Tired? The Borderline Markers Standard Panels Miss
Six markers that sit in the "technically normal" zone but are clinically linked to fatigue, brain fog, and low energy, ferritin, Vitamin D, TSH, B12, magnesium, and fasting glucose, and where the borderline zone for each one starts.
Optimal Blood Test Ranges vs. Normal: What's the Real Difference?
"Normal" means you fall inside 95% of a general population, not that a result is ideal. What functional-medicine "optimal" ranges claim, attributed to their sources, and what's actually evidence-backed.
Metabolic Optimization: What Your Blood Markers Actually Show
"Metabolic optimization" gets marketed as a lifestyle program. Underneath it, it's five to seven blood markers — glucose, HbA1c, fasting insulin, the lipid panel, and hs-CRP — and whether you're moving them is measurable.
Blood Tests for Fatigue: What to Ask For (and What Standard Panels Miss)
A thorough fatigue workup covers 4 cause clusters: iron status, thyroid function, blood sugar, and nutrients. Here are the specific tests in each cluster, why doctors often skip them, and a script for requesting them.
Blood Tests for Weight Loss: What to Check First
A handful of markers can flag a real obstacle, point you toward the diet that fits your body, or set a baseline to track. The evidence-based read on HbA1c, insulin, thyroid, iron, and vitamin D, plus the baseline labs before a GLP-1.
Blood Tests for Brain Fog: Which Markers to Check
The overlap between brain fog and fatigue is real, but the markers differ. Homocysteine, thyroid antibodies, fasting insulin, and B12 active fraction are the ones most likely missed on a standard workup.
Blood Tests for Low Mood & Depression: What to Ask For
Low mood and low motivation can have physical drivers. Thyroid, vitamin D, B12, folate, and iron are the markers worth ruling out before, or alongside, a mental health workup.
Blood Tests for Anxiety: What to Ask For
Anxiety can have physical drivers a standard panel misses, thyroid dysfunction, blood sugar swings, and magnesium deficiency among them. The tests to ask for before assuming it's purely psychological.
Blood Tests for Hair Loss: What to Ask For
Hair loss has multiple treatable causes that won't show on a standard panel. The specific tests to request, organized by which cause they rule in or out.
Blood Tests for Joint Pain: What to Ask For
Joint pain has several blood-test-detectable causes, inflammation, gout, and autoimmune disease among them. The markers to ask your doctor for and what each one rules in.
Blood Tests for Muscle Weakness & Cramps: What to Ask For
Muscle weakness and cramps often trace to vitamin D, magnesium, potassium, or thyroid. The blood tests that find the cause your standard panel won't flag.
Perimenopause Blood Test Results Explained
FSH, LH, estradiol, and AMH — what each result means, the reference ranges across the transition, and why a single test rarely confirms perimenopause.
Blood Tests for Cold Intolerance: What to Ask For
Always feeling cold can point to an underactive thyroid or iron deficiency. The tests to ask your doctor for before writing it off as "just your circulation."
Blood Tests for Dizziness: What to Ask For
Dizziness and light-headedness can come from anaemia, low blood sugar, or an electrolyte imbalance. The tests that separate one cause from another.
Blood Tests for Frequent Illness & Low Immunity: What to Ask For
Getting sick often or healing slowly can point to a vitamin D, iron, or B12 deficiency. The tests to ask for to find out which.
Blood Tests for Low Libido: What to Ask For
Low libido often has a hormonal or metabolic cause, testosterone, thyroid, iron, or blood sugar. The tests that find the actual driver.
Blood Tests for Poor Sleep: What to Ask For
Trouble falling or staying asleep can trace to magnesium, low iron stores, or an overactive thyroid. The tests worth asking for, and one worth trying before you test.
Blood Tests for Sugar Cravings: What to Ask For
Sugar cravings and afternoon crashes usually trace to blood sugar instability, not willpower. The tests that catch it before diabetes, and the two markers labs rarely add.
Blood Tests for Tingling and Numbness
Tingling in the hands or feet usually traces to B12 deficiency or diabetic nerve damage. The tests that find each, and what standard panels skip.
Blood Tests for Unexplained Weight Gain
Weight climbing without a diet or activity change usually points to thyroid or blood sugar. The tests that find out which, distinct from a weight-loss checklist.
Baseline Blood Test Panel: What to Check Yearly
No symptoms doesn't mean nothing to check. The 7 markers worth a yearly baseline, and why each catches a problem before it causes symptoms.
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FixFirst checks 130 biomarkers across 7 panels against clinical guidelines, flags borderline values standard ranges miss, and ranks your top 3 priorities — 45 seconds, free, no account.
Panel walkthroughs
Panel-by-panel guides to what each number means, what the reference ranges miss, and which values are worth watching closely.
How to Read Blood Test Results: A Plain-English Guide
What reference ranges actually measure, a 4-step framework for reading your results properly, and the 6 markers most commonly misread, including the borderline zones labs don't flag.
Translate Your Blood Test Results: What Every Abbreviation Means
A plain-English table of 40+ common abbreviations (CBC, metabolic panel, lipids, thyroid), what H and L flags mean, and how to spot patterns that point to a root cause.
How Long Do Blood Test Results Take? Turnaround by Test Type
A turnaround-time table by test type, why cultures and reference-lab tests take longer, ER vs GP timing, and when your doctor will actually call.
How to Read a CBC Blood Test: Step-by-Step Walkthrough
The most commonly ordered panel, but haemoglobin, MCV, RDW, and white cell differentials each tell a different story. What each value signals, and where the borderline zones start before anaemia is flagged.
CBC Blood Test: What Every Result Means
WBC, RBC, hemoglobin, hematocrit, MCV, MCH, MCHC, RDW, platelets, neutrophils, lymphocytes — what each number means, the ranges labs use, and which to act on first.
How to Read a Lipid Panel
LDL, HDL, triglycerides, and total cholesterol, what each number means on its own and why the ratio between them matters more than any single value. Plus what "high LDL" actually requires context to interpret.
How to Read a Comprehensive Metabolic Panel (CMP)
Kidney markers (creatinine, eGFR), liver enzymes (ALT, AST), electrolytes, and blood glucose, what each cluster is screening for and the values that warrant a closer look.
How to Read a Thyroid Panel (TSH, Free T3, Free T4)
Why TSH alone misses subclinical thyroid dysfunction, what Free T3 and Free T4 add that TSH can't show, and the values associated with persistent fatigue even when TSH prints as "normal."
TSH Blood Test: What Your Result Actually Means
TSH is the most-ordered thyroid test and the most misread. What high, low, and borderline results mean on their own, and what to do next.
Lipid Panel Blood Test: Which Number to Fix First
A standard lipid panel gives four numbers. Most labs flag one, rarely the most important. What each marker means and what to address first.
Comprehensive Metabolic Panel: 14 Markers, Ranked
A CMP reports 14 markers. Which ones actually signal a problem early, how reference ranges differ from optimal, and what to address first.
Liver Function Blood Test: What ALT, AST, GGT, and ALP Mean
ALT, AST, ALP, GGT, bilirubin, albumin — what each liver marker means, which to address first, and when an elevated result needs follow-up.
Does Dehydration Affect Blood Test Results?
Dehydration concentrates your blood, raising BUN, creatinine, sodium, and hematocrit. Which markers shift, by how much, and how to retest it right.
Urea and Electrolytes (U&E) Blood Test Results Explained
Sodium, potassium, urea, creatinine, chloride, bicarbonate and eGFR — the standard NHS kidney and fluid-balance panel, explained marker by marker.
Full Blood Count (FBC) Interpretation: Results Explained
Haemoglobin, white cells, platelets, MCV — the most commonly ordered blood test in the UK, explained in plain English with what high and low results mean.
Deep dives
Individual guides to the markers that come up most often, what a high or low result means, what the borderline zone looks like, and what to do about it. For markers where longevity-focused physicians and researchers cite their own optimal targets, see the Longevity blood markers section, each target attributed to its source.
UIBC Blood Test: What High and Low Results Mean
UIBC measures the unused iron-binding capacity in your blood. High UIBC points to iron deficiency. Low UIBC suggests iron overload. Normal range, causes, and what to do next.
Low Ferritin: What It Means, Symptoms, and What to Do
Ferritin depletes months before haemoglobin drops, meaning a normal CBC doesn't rule it out. The borderline zone, what symptoms to expect, causes, and what to do about it.
Low Vitamin D: Why Labs Miss It and What to Fix
The NIH flags insufficiency at 20–29 ng/mL. Most labs only flag below 20. That gap, where millions of results land, is where fatigue, low mood, and immune suppression commonly show up.
High LDL Cholesterol: What It Actually Means for You
LDL above range is not uniform risk. Context, your HDL ratio, triglycerides, family history, and diet, changes the picture significantly. The ACC/AHA classification and when to act.
Low Vitamin B12: Symptoms, Causes, and What to Do
NICE identifies a neurological risk zone at 140–220 pg/mL — below the standard flag threshold. Fatigue, tingling, and brain fog can appear here. The absorption vs. intake distinction determines whether oral supplements will work.
High TSH: What It Means, Symptoms, and When to Act
The normal range goes up to 4.5 mIU/L, but many patients report fatigue, cold intolerance, and brain fog above 2.5. What TSH is actually measuring, the Hashimoto's connection, and what a full thyroid panel includes.
High Triglycerides: What the Number Means and How to Bring It Down
Triglycerides are the most diet-responsive marker on a standard lipid panel, and a stronger insulin resistance signal than LDL alone. Primarily driven by sugar and refined carbs, not dietary fat. 20–50% reductions in 4–8 weeks with targeted changes.
High HbA1c: What It Means and How to Lower It
HbA1c is a 3-month average of blood sugar control. The ADA prediabetes range starts at 5.7%. Here's what different values signal, what lifestyle changes move the needle, and how fast improvement shows up.
HbA1c Blood Test: What Your Result Means
HbA1c measures your 3-month average blood sugar. Here's what normal, prediabetes, and diabetes ranges mean — and the optimal zone most labs don't flag but matters for long-term health.
Fasting Insulin: The Test Not on Your Panel
Fasting insulin is the earliest marker for insulin resistance, often abnormal years before HbA1c flags anything. What the test measures and how to request it.
CRP Blood Test: What a High Result Actually Means
A high CRP confirms inflammation but not its cause. How to interpret your result in context, hs-CRP bands, ESR, ferritin, and acute vs. chronic patterns.
High Creatinine: What It Means and What Else Raises It
High creatinine doesn't always mean kidney disease. Creatine supplements, high protein intake, and dehydration all raise it. How to tell the difference.
Low Magnesium: Why Serum Isn't the Right Marker
Low magnesium symptoms appear before a standard blood test flags anything. Why serum is unreliable, what to test instead, and what low levels cause.
Segmented Neutrophils: What Your Count Actually Means
The percentage on your differential isn't the number clinicians act on. How to calculate absolute neutrophil count, and why a low count is normal physiology for millions of people (DANC).
Progesterone in Men: What Your Level Means
Low is the normal male result, not a deficiency. Why no guideline body publishes a male target, what actually raises it, and the markers that better explain low libido or fatigue.
Pattern recognition
Some abnormal pairings aren't a coincidence — they share a root cause. What the combination usually means and which one to address first.
High TSH and Low Ferritin: The Thyroid-Iron Connection
High TSH and low ferritin appearing on the same test is rarely a coincidence. Hypothyroidism directly impairs iron absorption. The mechanism, the right priority order, and what to ask your doctor.
Low Ferritin and High Cholesterol: Why They Often Appear Together
These two markers frequently flag together for the same root cause, often thyroid dysfunction. What the pairing means and what to address first.
High TSH and High LDL: The Thyroid-Cholesterol Link
An underactive thyroid slows how fast the liver clears LDL, so cholesterol rises with the TSH. Why checking thyroid can precede a statin, and what to do first.
High Glucose and High Triglycerides: The Insulin Resistance Link
Both flags are downstream of one problem: cells that no longer respond to insulin. Treat the root cause and both numbers move, with triglycerides usually falling first.
High MCV and Low B12: The Macrocytosis Connection
A raised MCV with low B12 is one finding, not two. B12 deficiency enlarges red blood cells, and the reason to act quickly is your nerves, not your blood count.
High RDW and Low MCV: The Iron Deficiency Pattern
High RDW with low MCV is the classic iron deficiency anaemia pattern, and the test that tells it apart from thalassemia trait, which looks the same on MCV alone.
Multiple Abnormal Results? 64% of Healthy People Get One
On a 20-marker panel, a healthy person has roughly a 64% chance of at least one abnormal flag by statistics alone. How to tell which of yours actually matter.
4 Signals to Rank Your Abnormal Blood Test Results
Multiple flags, no priority order? Four signals, magnitude, clustering, symptom match, and persistence, decide which abnormal result to fix first.
Abnormal Blood Test Results: Next Steps Guide
Got abnormal results and not sure what to do? What to do next, from reading the flags to knowing when to act urgently vs. monitor.
Longevity
Peter Attia, Andrew Huberman, and other longevity-focused physicians and researchers publish their own targets for specific markers. Each one is attributed to the person who cited it, not a FixFirst recommendation.
Longevity Blood Markers
The section landing page: what it covers, how it's attributed, and links to every expert-cited page below.
Peter Attia's Blood Test Panel
16 markers across metabolic health, lipids, inflammation, liver, kidney, and hormones, with the targets Attia has cited on The Drive.
Andrew Huberman's Blood Test Markers
Vitamin D, testosterone, ApoB, and cortisol timing, the markers Huberman covers most often, and the targets he cites.
Bryan Johnson's Blood Test Panel
ApoB, HbA1c, hs-CRP, fasting insulin, vitamin D, and ferritin, the reported targets from Blueprint, cross-checked across independent sources.
Optimal IGF-1 Level
Why longevity researchers disagree: Valter Longo's lower-is-better case versus Peter Attia's balance framing, and where growth hormone peptides fit in.
Peptides & Hormones
A different kind of guide: what to test before and after starting a hormone or peptide therapy, and how to read the change. These are medically reviewed and anchored to clinical guidelines, not expert-protocol opinion. What to test, never how to dose or where to source.
Peptides & Hormones
The section landing page: what before-and-after monitoring covers, and links to every therapy guide below.
TRT Before & After Blood Work
The testosterone-therapy monitoring panel, anchored to AUA and Endocrine Society guidance. Why hematocrit, not testosterone, is the marker that governs safety.
GLP-1 Before & After Blood Work
Semaglutide, tirzepatide, and similar. The markers worth tracking beyond glucose, anchored to FDA labeling and the ADA Standards of Care.
Sermorelin Before & After Blood Work
A growth-hormone secretagogue: the established GH-axis and safety markers to track. Off-label in adults, and on the WADA banned list for athletes.
Comparisons
How FixFirst compares to general-purpose AI and other blood test platforms, on the cases that matter.
Best AI Blood Test Analyzers (2026): An Honest Roundup
Seven tools scored on the same criteria — cost, whether they work with labs you already have, priority ranking, and clinical thresholds. Free analyzers, paid analyzers, and testing services, with who each one fits.
FixFirst vs ChatGPT: Blood Test Analysis Compared
5 specific failure modes where general AI misses: sex-adjusted thresholds, borderline zones, priority ranking across multiple abnormal markers, guideline-anchored recommendations, and consistent output. With a direct comparison table.
FixFirst vs InsideTracker: Which Is Right for You?
InsideTracker runs its own tests and builds a longitudinal picture. FixFirst analyzes blood work you already have. The comparison covers cost, depth, use cases, and who each platform actually serves best.
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