Site Map
Interactive tools
- Sunlight Calculator
Estimate how much vitamin D your body makes from sun exposure.
- Latent Vitamin D Reserves Calculator
Model your stored cholecalciferol through winter.
- Blood Test Interpreter
Understand your serum 25(OH)D result.
- Unit Converter
IU ↔ µg and ng/mL ↔ nmol/L.
Guides & deep dives
- Complete Vitamin D Guide
Everything you need to know in one place.
- How the Calculator Works
The physics and physiology behind the math.
- Vitamin D Winter
Latitude, UVB, and seasonal deficiency.
Reference articles
- Benefits (evidence-ranked)
What the clinical trials really show.
- Deficiency Symptoms
Nine signs your 25(OH)D may be low.
- Dosage Guide
RDA, UL, and repletion protocols.
- Toxicity & Safe Upper Limits
Can you take too much?
- Vitamin D and Immunity
Cathelicidin, T-cell modulation, RCT evidence.
- Vitamin D and Osteoporosis
Bone density, fractures, and evidence-based dosing.
- Vitamin D and Sun Safety
UVB benefits vs. skin-cancer risk.
- Vitamin D and Hair Loss
Alopecia areata, telogen effluvium.
- Vitamin D and Weight Loss
What the evidence really shows.
- Best Time of Day
Sun timing vs. supplement timing.
- How Long to Raise 25(OH)D
Dose-response and time-to-steady-state.
- D + Magnesium + K2
Cofactor stacking, evidence.
- Vitamin D vs D3
D3 vs D2 explained.
- Vitamin D Half-Life
Pharmacokinetics and body-composition effects.
- Vitamin D in Older Adults
Falls, fractures, and dosing after 65.
- Vitamin D and Mental Health
Depression, SAD, anxiety evidence.
- How to Take Vitamin D
Drops vs capsules, timing, cofactors.
- Testing Guide
What to order, how to prep, how to interpret.
- Vitamin D and Diabetes
Type 2 prevention, insulin sensitivity.
- Vitamin D and Testosterone
Male hormone effects, evidence-based.
- Vitamin D and Thyroid
Hashimoto's, Graves', TPO antibodies.
- Vitamin D and Sleep
Sleep quality, insomnia, OSA.
- Vitamin D for Vegans
Lichen D3, D2, and plant sources.
- Absorption Issues
Malabsorption, meds, and bariatric surgery.
- Vitamin D and PCOS
Insulin, ovulation, fertility.
- Vitamin D and Heart Health
BP, CVD events, VITAL trial.
- Vitamin D and Cancer
Incidence, mortality, type-by-type evidence.
- Cognitive Decline
Dementia and Alzheimer's risk.
- Psoriasis & Eczema
Topical calcipotriene, UVB, oral adjunct.
- Fibromyalgia & Chronic Pain
Osteomalacia mimic, chronic pain.
- All Vitamins & Minerals
Complete reference index.
- Vitamin B12
Cobalamin deficiency and treatment.
- Vitamin C
Ascorbic acid — collagen and immunity.
- Vitamin A
Retinol vs beta-carotene, toxicity.
- Vitamin E
Alpha-tocopherol antioxidant reference.
- Vitamin K
K1 clotting, K2 bone and vascular.
- Folate (B9)
Neural tube defects, MTHFR.
- Magnesium
Enzyme cofactor, forms compared.
- Iron
Anaemia, heme vs non-heme.
- Zinc
Immunity, wound healing, cold lozenges.
- Calcium
Bone density, carbonate vs citrate, food-first.
- Omega-3 (EPA & DHA)
Cardiovascular RCTs, algae oil, dosing.
- Choline
Brain, liver, and the AI 90% miss.
- Vitamin B6
PMS, morning sickness, neuropathy risk.
- Vitamin B1 (Thiamine)
Beriberi, Wernicke-Korsakoff, refeeding.
- Vitamin B3 (Niacin)
Pellagra, cholesterol, NAD+ precursors.
- Biotin (B7)
Hair, nails, and lab-test interference.
- Selenium
Thyroid, SELECT trial, brazil nut caution.
- Vitamin D and COVID-19
Observational signal vs RCT reality.
- Vitamin D and MS
Latitude gradient and MR evidence.
- Vitamin D and Asthma
Exacerbations, Cochrane, VDAART.
- Vitamin D and Acne
The deficiency link and RCT evidence.
- Vitamin B2 (Riboflavin)
Migraine prophylaxis, MTHFR, yellow urine.
- Vitamin B5 (Pantothenic Acid)
CoA, acne claim, panthenol.
- Potassium
DASH, salt substitutes, hyperkalaemia ceiling.
- Iodine
Thyroid, pregnancy, kelp overdose risk.
- Vitamin D and IBD
Crohn's & UC — deficiency and dosing.
- Vitamin D and Migraine
Attack frequency, riboflavin stacking.
- Vitamin D and Eczema
Winter flares, cathelicidin, RCT evidence.
- Vitamin D and RA
DAS28, VITAL prevention, DMARD adjunct.
- Vitamin D and Lupus
Photosensitivity paradox, SLEDAI evidence.
- Vitamin D and COPD
ViDiCO trial, deficient-subgroup benefit.
- Vitamin D and CKD
CKD-MBD, calcitriol vs paricalcitol.
- Vitamin D and Liver
NAFLD, cirrhosis, calcifediol.
- Vitamin D and Dental
Caries, periodontitis, implants.
- Vitamin D and Eyes
AMD, dry eye, retinopathy.
- Vitamin D for Athletes
Performance, stress fractures.
- Vitamin D for Men
Testosterone, sperm, muscle, prostate.
- Vitamin D for Women
Bones, pregnancy, PCOS, menopause.
- Loading Dose Protocols
50,000 IU weekly regimens.
- Daily vs Weekly Dosing
Cadence, compliance, outcomes.
- UV Lamps for Vitamin D
Which lamps actually work.
- Vitamin D and Shift Work
Night-shift and indoor jobs.
- Vitamin D and Skin Color
Fitzpatrick types, synthesis gap.
- Vitamin D and Long COVID
Observational data and dosing.
- Copper
Ceruloplasmin, Wilson's, zinc trap.
- Chromium
Blood-sugar claims, EFSA verdict.
- Manganese
MnSOD; manganism from excess.
- Molybdenum
Sulfite oxidase cofactor.
- Fluoride
Water fluoridation, caries, fluorosis.
- Vitamin D and Hashimoto's
TPO antibody reduction.
- Vitamin D and Endometriosis
Pain scores, dosing.
- Vitamin D and Fertility
IVF, sperm, pre-conception.
- Vitamin D and IBS
IBS-SSS trials.
- Vitamin D and Back Pain
Osteomalacia mimicry.
- Vitamin D and Gout
Uric acid data.
- Vitamin D and ADHD
Adjunctive trials.
- Vitamin D and Autism
Prenatal and ASD trials.
- Vitamin D and Chronic Pain
Pain-clinic deficiency.
- Vitamin D and Vitiligo
Calcipotriene, NB-UVB.
- Vitamin D and Alopecia Areata
SALT score, topical, JAKi.
- Vitamin D and Cystic Fibrosis
CFF targets, malabsorption.
- Vitamin D After Bariatric
ASMBS post-op dosing.
- Vitamin D and Menopause
Bone loss, falls, HRT.
- Vitamin D with Magnesium
Cofactor for activation.
- Drops vs Capsules vs Sprays
Formulation comparison.
- Vitamin D and Obesity
BMI-based dosing, dilution.
- Drug Interactions
Anticonvulsants, steroids, thiazides.
- Vitamin D and Alcohol
Hepatic deficiency, bones.
- Vitamin D and Breast Cancer
VITAL/WHI, survival, AI arthralgia.
- Vitamin D and Colorectal Cancer
SUNSHINE, adenoma prevention.
- Vitamin D and Prostate Cancer
Marshall trial, ADT bones.
- Vitamin D and Skin Cancer
BCC, SCC, melanoma trade-off.
- Vitamin D and Parkinson's
UPDRS, VDR biology.
- Vitamin D and Flu
Martineau meta-analysis.
- Vitamin D and GDM
DALI trial.
- Vitamin D for Infants
AAP 400 IU.
- Vitamin D and Preterm Birth
Maternal supplementation trials.
- Vitamin D by Month
The UVB annual cycle.
- Vitamin D and Cloud Cover
How clouds reduce UVB.
- What You're Wearing
Coverage, UPF, cultural dress.
- Vitamin D by Latitude
City-by-city vitamin D winter.
- Vitamin D and Climate
Climate types & deficiency.
- Through a Window
Glass blocks UVB.
- Vitamin D and Sunscreen
SPF myths and reality.
- Air Pollution and UVB
Smog and wildfire smoke.
- Vitamin D and Altitude
Elevation and snow reflection.
- Time of Day and Vitamin D
Shadow rule, 35° threshold.
- Complete Supplementation Guide
7-step dosing walkthrough.
- Vitamin D and SAD
Two different winter problems.
- Vitamin D and Vacation
Sunny trip impact.
- Hot and Desert Climates
Sunny but deficient populations.
- Supplement Buyer's Guide
Testing, value, red flags.
- Humidity
Small UVB effect.
- Tanning Beds
Melanoma trade-off.
- Shade
Umbrella and canopy transmission.
- Meal Plan Ideas
Sample days to hit RDA from food.
- Vitamin D and Fatigue
When correction actually helps.
- Common Cold
Prevention evidence.
- Headaches (non-migraine)
Tension, cluster, cervicogenic.
- Vitamin D in the UK
PHE, winter deficiency.
- Vitamin D in Canada
Health Canada, fortification.
- Vitamin D in Australia
Cancer Council balance.
- Vitamin D in the US
IOM vs Endocrine Society.
- Vitamin D in India
Sun-rich, deficient paradox.
- Vitamin D in Scandinavia
Cod liver oil, polar night.
- Vitamin D in Middle East
Sunniest, most deficient.
- Birth Control
Estrogen-DBP effect.
- Statins (SAMS)
Muscle symptom rescue.
- Vaccine Response
Antibody titre evidence.
- Metabolic Syndrome
Insulin resistance, HDL.
- Hypertension
RAAS, MR, VITAL.
- Erectile Dysfunction
Endothelial function link.
- Vitamin D and Caffeine
Coffee and bone health.
- Vitamin D and Smoking
Smokers run lower.
- Outdoor Workers
Sun-exposed but deficient.
- Vitamin D for Teens
Peak bone-mass window.
- Vitamin D and COVID Severity
Hospital trial evidence.
- Hyperparathyroidism
Primary vs secondary.
- Sarcoidosis
Hypercalcaemia risk.
- Hearing Loss
BPPV, SSNHL, presbycusis.
- Tinnitus
Small trial evidence.
- Rosacea
Cathelicidin complication.
- Restless Legs (RLS)
Iron first, then vitamin D.
- Post-Surgery Recovery
Wound and infection outcomes.
- Dialysis
Active analogues, KDIGO.
- Dementia
MR and VITAL cognitive substudy.
- Anxiety
GAD-7 trial signal.
- Recurrent Miscarriage
RPL workup.
- Birth Defects
Safety margin.
- HPV
Clearance and vaccine.
- Atopic March
VDAART, COPSAC.
- Glucocorticoid Users
GIOP prevention.
- Heart Failure
VINDICATE trial.
- Atrial Fibrillation
AF risk pattern.
- Postpartum Depression
EPDS evidence.
- Athletic Performance
Elite screening and dosing.
- Immune Mechanisms Deep Dive
Cathelicidin, T-cells, macrophages.
- Kidney Stones
Calcium-oxalate paradox.
- Lyme Disease
PTLDS deficiency signal.
- Tuberculosis
Sanatorium and modern trials.
- Immunosuppression
Transplant, biologics, HIV.
- PPI Users
B12, calcium, fracture, citrate.
- Metformin
B12 depletion.
- Thyroid Cancer
Post-thyroidectomy care.
- Kid Sun Safety
Play, sunscreen, prevention.
- Lactation
Wagner-Hollis 6,400 IU option.
- Brain Fog
Differential and correction.
- Dry Eye Disease
OSDI improvement trials.
- Childhood Eczema
Camargo RCT, winter flares.
- Vitamin D in Pregnancy
Requirements and risks for expectant mothers.
- Vitamin D for Kids
Infants, children, and adolescents.
- Foods High in Vitamin D
Searchable table with IU per serving.
Reference
- Frequently Asked Questions
18 answered questions.
- Glossary
Terminology and abbreviations.
- About
Methodology and site background.
- Contact
Feedback and inquiries.