Introduction

You're tired all the time. Your mood is off. You catch every cold that goes around. And despite doing "everything right," something still feels wrong.

Here's what most doctors won't tell you: 42% of Americans are deficient in vitamin D, with levels below 20 ng/mL. Many more have suboptimal levels below 30 ng/mL.

The critical detail-vitamin D isn't just a vitamin. It's a hormone that regulates over 200 genes in your body. Low vitamin D affects everything from energy and mood to bone health, immune function, and longevity.

The good news? Raising your vitamin D levels naturally is straightforward when you understand the science.

In this guide, you'll discover:

• Why vitamin D matters for health and longevity

• 7 evidence-based methods to optimize your levels naturally

• Optimal dosing protocols based on your current levels

• Testing frequency and target ranges from preventive health experts

• Common mistakes that prevent vitamin D optimization

Want to check your vitamin D status? Our comprehensive vitamin panel gives you accurate 25-hydroxyvitamin D levels-the gold standard for assessment. Prevention over intervention starts with knowing your numbers.

The Science

Vitamin D3 (cholecalciferol) is converted in your liver to 25-hydroxyvitamin D [25(OH)D], the form measured in blood tests. This is then converted to the active hormone calcitriol in your kidneys and other tissues.

What Optimal Vitamin D Can Do For You

• Bone Health: Supports calcium absorption and bone remodeling

• Immune Function: Helps modulate innate and adaptive immunity

• Mood & Cognitive Function: Influences serotonin production

• Cardiovascular Health: Can help reduce inflammation and support blood pressure regulation

• Longevity: Associated with reduced all-cause mortality

• Muscle Function: Critical for strength and performance

• Metabolic Health: Can improve insulin sensitivity

What Happens With Low Vitamin D

• Fatigue and low energy

• Frequent infections

• Mood changes, depression

• Bone pain and muscle weakness

• Slow wound healing

• Hair loss

• Increased cardiovascular risk

Standard Lab Ranges vs. Optimal

• Deficient: <20 ng/mL (50 nmol/L) - Clinical deficiency

• Insufficient: 20-30 ng/mL (50-75 nmol/L) - Standard "normal"

• Adequate: 30-40 ng/mL (75-100 nmol/L) - Conventional target

• Optimal: 40-60 ng/mL (100-150 nmol/L) ← Longevity experts target

• High: 60-80 ng/mL (150-200 nmol/L) - Monitor closely

• Toxic: >100 ng/mL (>250 nmol/L) - Requires medical intervention

Expert Recommendations

• Peter Attia: Targets 40-60 ng/mL for patients

• Bryan Johnson: Maintains 50-60 ng/mL year-round

• Andrew Huberman: Recommends 40-50 ng/mL minimum

• Rhonda Patrick: Suggests 40-60 ng/mL, up to 80 ng/mL acceptable

The reality? Most people need 40+ ng/mL for optimal health-not just 30 ng/mL (the conventional "adequate" threshold). when you optimize your levels.

Track Your Vitamin D Levels

Mito Health tests 100+ biomarkers including 25-hydroxyvitamin D, PTH, and calcium with physician-guided protocols to help you optimize immunity, bone health, and longevity. Our comprehensive panels provide personalized interpretation to identify deficiency early.

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The Science

Your skin produces vitamin D3 when UVB rays (290-320 nm wavelength) hit 7-dehydrocholesterol in your skin. This is the most efficient way to raise vitamin D-when done correctly.

How Much Sun Exposure You Need

Fair Skin (Fitzpatrick I-II):

• Summer: 10-15 minutes midday, 25% body exposed (arms, legs)

• Winter: 30-40 minutes midday (if UVB available in your latitude)

• Produces: ~10,000-20,000 IU per session

Medium Skin (Fitzpatrick III-IV):

• Summer: 15-25 minutes midday, 25% body exposed

• Winter: 45-60 minutes midday

• Produces: ~8,000-15,000 IU per session

Dark Skin (Fitzpatrick V-VI):

• Summer: 30-45 minutes midday, 25% body exposed

• Winter: 60-90 minutes midday (often insufficient)

• Produces: ~5,000-10,000 IU per session

• Note: Dark skin requires 3-6x more sun exposure; supplementation often necessary

Best Practices

1. Timing: 10am-2pm (when UVB is strongest)

2. Latitude matters: Above 37° latitude (San Francisco, Denver, Philadelphia), winter sun produces minimal vitamin D (Nov-Feb)

3. No sunscreen initially: Blocks UVB; apply after 10-30 minutes for cancer protection

4. Never burn: Stop before skin turns pink

5. Consistency: 3-5x per week is more effective than occasional long sessions

Limitations

• Geography: Northern latitudes lack UVB in winter

• Season: October-March yields little vitamin D above 35° latitude

• Skin tone: Darker skin needs significantly more exposure

• Age: Production decreases 50% by age 65

• Practical: Many people can't access midday sun regularly

The takeaway: Sun exposure is ideal in summer but insufficient for most people in winter. Combine with other methods.

Why Vitamin D3 (Cholecalciferol)?

• D3 vs. D2: D3 is 87% more effective at raising blood levels

• Always choose D3 (not D2/ergocalciferol)

• Source: Animal-derived (lanolin) or vegan (lichen)

Dosing Protocols by Current Level

If You're Deficient (<20 ng/mL):

• Loading dose: 10,000 IU daily for 4-8 weeks

• Then: Retest and adjust to maintenance

• Medical note: Some doctors prescribe 50,000 IU weekly x 8 weeks

If You're Insufficient (20-30 ng/mL):

• Correction dose: 5,000-7,000 IU daily for 8-12 weeks

• Then: Retest and adjust to maintenance

If You're Adequate But Want Optimal (30-40 ng/mL):

• Optimization dose: 4,000-5,000 IU daily for 12 weeks

• Then: Retest and adjust to maintenance

Maintenance Dose (Once at 40-60 ng/mL):

• General maintenance: 2,000-4,000 IU daily

• Individual variation: Some need 5,000+ IU to maintain

• Rule of thumb: 1,000 IU raises levels ~5-10 ng/mL over 3 months

• Retest: Every 3-6 months to dial in your personal dose

Absorption Tips

• Take with fat: Vitamin D is fat-soluble; take with meals containing healthy fats

• Best timing: Morning with breakfast (mimics natural sun exposure, may support circadian rhythm)

• Consistent daily dosing is better than large weekly doses

Quality Matters

• Look for third-party tested (NSF, USP, ConsumerLab)

• Check for purity (no synthetic fillers)

• Oil-based softgels absorb better than dry tablets

Method 3 - Vitamin D + Cofactors (Maximize Absorption & Safety)

Taking vitamin D alone isn't optimal. Key cofactors enhance absorption and prevent depletion of other nutrients.

Vitamin K2 (MK-7) - Essential Partner

Why: Vitamin D increases calcium absorption, but K2 directs calcium to bones (not arteries)

• Dose: 100-200 mcg K2-MK7 daily with vitamin D

• Function: Activates proteins that bind calcium to bone matrix

• Safety: Prevents arterial calcification (especially at higher D3 doses)

Not sure which vitamin D form to choose? Our complete vitamin D form comparison breaks down D2 vs D3 vs D3+K2 combinations.

Peter Attia's Take: "I never give vitamin D without K2. It's malpractice."

Magnesium - The Activation Cofactor

Why: Vitamin D activation requires magnesium-dependent enzymes

• Dose: 300-500 mg elemental magnesium daily

• Forms: Glycinate (best absorption, no laxative effect) or threonate (brain health)

• Function: Converts vitamin D to its active form (calcitriol)

• Sign you need it: Taking vitamin D but levels stay low

Optimal Stack

Morning with breakfast (fat-containing meal): - Vitamin D3: 4,000-5,000 IU (adjust based on levels) - Vitamin K2-MK7: 100-200 mcg - Magnesium glycinate: 300-400 mg (or split dose, remainder at night)

Other Supportive Nutrients

• Boron: 3-6 mg (enhances vitamin D metabolism)

• Zinc: 15-30 mg (synergistic with vitamin D for immune function)

• Omega-3s: Support vitamin D receptor function

Ready to optimize your protocol? Get tested to understand your vitamin D, cofactor levels, and build your personalized supplement stack. Prevention over intervention starts with data.

Food Sources of Vitamin D

While food alone rarely achieves optimal levels, it's supportive:

Best Sources (IU per serving):

• Salmon, wild-caught (3.5 oz): 600-1,000 IU

• Salmon, farmed (3.5 oz): 100-250 IU

• Sardines, canned (3.5 oz): 300 IU

• Mackerel (3.5 oz): 360 IU

• Tuna, canned (3.5 oz): 230 IU

• Cod liver oil (1 tbsp): 1,360 IU

• Egg yolks (1 large): 40 IU

• Beef liver (3.5 oz): 50 IU

• Fortified milk (1 cup): 100 IU

• Fortified orange juice (1 cup): 100 IU

• Mushrooms, UV-exposed (3.5 oz): 400-1,000 IU

Photo from Unsplash

The Reality

To get 4,000 IU from food alone, you'd need:

• 4 servings of wild salmon daily, or

• 3 tablespoons of cod liver oil daily (not practical)

Conclusion: Food sources are supportive but insufficient. Sun + supplementation needed.

When to Test

• Baseline: Test before starting optimization

• Follow-up: Retest after 8-12 weeks of intervention

• Maintenance: Every 3-6 months once optimized

• Seasonal: Test winter vs. summer to see variation

What to Test

Primary:

• 25-hydroxyvitamin D [25(OH)D] - This is the standard vitamin D test

Advanced (Optional):

• Parathyroid hormone (PTH): Should decrease as vitamin D rises (optimal: 15-30 pg/mL)

• Calcium, serum: Monitor if taking high-dose D3 (optimal: 9.0-10.2 mg/dL)

• Magnesium, RBC: More accurate than serum magnesium (optimal: 5.0-6.5 mg/dL)

Interpreting Your Results

**Current Level and Action Plan:** Less than 20 ng/mL: 10,000 IU daily for 4-8 weeks 20-30 ng/mL: 5,000 IU daily for 8-12 weeks 30-40 ng/mL: 4,000 IU daily for 12 weeks 40-60 ng/mL: Maintain with 2,000-4,000 IU daily Above 60 ng/mL: Reduce or pause supplementation, retest in 4 weeks

Testing Options

• Lab draw: Quest, LabCorp (via doctor or direct-to-consumer)

• At-home fingerprick: Everlywell, LetsGetChecked (convenient but less accurate)

• Comprehensive panel: Mito Health (includes D, K2, magnesium, PTH, calcium, and 140+ biomarkers)

[CTA: Book Your Test -> Check your vitamin D levels and get a personalized optimization plan]

Weight Management

• Obesity reduces bioavailability: Vitamin D is fat-soluble and gets sequestered in adipose tissue

• Impact: Obese individuals need 2-3x more vitamin D to achieve optimal levels

• Solution: Increase dosing or focus on weight loss alongside supplementation

Gut Health

• Absorption: Vitamin D is absorbed in the small intestine

• Issues: IBS, Crohn's, celiac disease, or leaky gut reduce absorption

• Support: Heal gut lining, optimize digestion, consider liposomal D3 if malabsorption suspected

Liver & Kidney Function

• Conversion: Liver converts D3 to 25(OH)D; kidneys convert to active calcitriol

• Testing: If supplementing but levels stay low, check liver enzymes (ALT, AST) and kidney function (creatinine, eGFR)

Stress & Cortisol

• Chronic stress: Impairs vitamin D receptor function

• Support: Manage stress with breathwork, meditation, sleep optimization

Circadian Rhythm

• Vitamin D receptors: Follow circadian patterns

• Optimization: Morning supplementation may align better with natural rhythms

UVB Phototherapy (For Winter)

• UVB lamps: 290-320 nm wavelength (not tanning beds)

• Usage: 5-10 minutes, 2-3x per week

• Brands: Sperti Vitamin D Lamp (FDA-approved)

• Produces: Similar to sun exposure

• Caution: Risk of skin damage; monitor carefully

Higher-Dose Protocols (Medical Supervision)

Some practitioners use:

• 50,000 IU weekly for deficiency correction

• 10,000-20,000 IU daily short-term under monitoring

• Requires: Regular blood testing for calcium, PTH, 25(OH)D

Note: Stay at 10,000 IU or below without medical supervision.

Vitamin D Analogs (Prescription)

• Calcitriol: Active form, used for specific medical conditions

• Not for general use: Risk of hypercalcemia

Optimize From Within

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Mistake 1 - Not Testing

Problem: Guessing your dose leads to under- or over-supplementation
Solution: Test baseline, then every 3 months until optimized

Mistake 2 - Taking D3 Without K2

Problem: Risk of arterial calcification, especially at higher doses
Solution: Always pair D3 with K2-MK7 (100-200 mcg)

Mistake 3 - Ignoring Magnesium

Problem: Vitamin D can't be activated without magnesium; causes depletion
Solution: Take 300-500 mg magnesium daily

Mistake 4 - Taking Vitamin D at Night

Problem: May disrupt sleep (anecdotal; not proven for everyone)
Solution: Take in the morning with breakfast

Mistake 5 - Stopping Too Soon

Problem: Vitamin D rises slowly; levels stabilize after 3+ months
Solution: Stay consistent, retest at 8-12 weeks

Mistake 6 - Relying Only on Sun in Winter

Problem: UVB is insufficient above 35° latitude from October-March
Solution: Supplement 4,000-5,000 IU daily in winter

Mistake 7 - Not Accounting for Body Weight

Problem: Heavier individuals need more vitamin D
Solution: Adjust dosing: 40-50 IU per kg body weight for maintenance

Step 1 - Test Your Current Levels

Get a 25(OH)D blood test to establish baseline.

Step 2 - Calculate Your Starting Dose

Use the guidelines above based on your current level.

Step 3 - Add Cofactors

• Vitamin K2-MK7: 100-200 mcg

• Magnesium glycinate: 300-500 mg

Step 4 - Implement Sun Exposure (If Possible)

• 10-30 minutes midday, 3-5x per week (summer)

• Adjust for skin tone and latitude

Step 5 - Retest in 8-12 Weeks

See if you're reaching 40-60 ng/mL. Adjust dose as needed.

Step 6 - Maintain & Monitor

Once optimized, maintain with 2,000-4,000 IU daily and retest every 6 months.

Subjective Markers of Improvement (2-8 weeks)

• Increased energy and reduced fatigue

• Improved mood and reduced brain fog

• Stronger immune function (fewer colds)

• Better sleep quality

• Reduced muscle aches or joint pain

Objective Markers (Blood Work)

• 25(OH)D: 40-60 ng/mL (primary target)

• PTH: 15-30 pg/mL (should drop as D rises)

• Calcium: 9.0-10.2 mg/dL (stable)

The Bottom Line

Raising vitamin D levels naturally combines:

1. Strategic sun exposure (when available)

2. Daily D3 supplementation (4,000-5,000 IU to start)

3. Essential cofactors (K2, magnesium)

4. Regular testing (every 3-6 months)

5. Lifestyle optimization (weight, gut health, stress management)

Target: 40-60 ng/mL for optimal health and longevity.

Don't guess-test. Most people need 4,000-5,000 IU daily to maintain optimal levels year-round, but individual variation is significant. The only way to know your ideal dose is through regular blood testing.

Ready to optimize? Our comprehensive vitamin panel checks vitamin D, K2, magnesium, PTH, calcium, and 140+ other biomarkers-giving you complete data-driven insights. Individual testing at $349, comprehensive duo testing at $668.

Key Takeaways

Optimal vitamin D is 40-60 ng/mL, not just 30 ng/mL
Most people need 4,000-5,000 IU daily to reach and maintain optimal levels
Always pair D3 with K2 and magnesium for safety and effectiveness
Test every 3-6 months to dial in your personal dose
Sun exposure helps but isn't sufficient for most people (especially winter)
It takes 8-12 weeks to see meaningful changes in blood levels

Related Content

• Which Vitamin D Form

• Magnesium + D Synergy

• Vitamin D + Omega-3

Medical Disclaimer

This article is for educational and informational purposes only and does not constitute medical advice. The information provided should not be used for diagnosing or treating a health condition. Always consult with your doctor or qualified healthcare provider before starting any new supplement protocol, making changes to your diet, or if you have questions about a medical condition.

Individual results may vary. The dosages and protocols discussed are evidence-based but should be personalized under medical supervision, especially if you have existing health conditions or take medications.

References

1. Holick MF. Vitamin D deficiency. N Engl J Med. 2007;357(3):266-81. PMID: 17634462 | DOI: 10.1056/NEJMra070553

2. Pludowski P, Holick MF, Grant WB, et al. Vitamin D supplementation guidelines. J Steroid Biochem Mol Biol. 2018;175:125-135. PMID: 28216084 | DOI: 10.1016/j.jsbmb.2017.01.021

3. Heaney RP. Vitamin D in health and disease. Clin J Am Soc Nephrol. 2008;3(5):1535-41. PMID: 18525006 | DOI: 10.2215/CJN.01160308

4. Patrick RP, Ames BN. Vitamin D and the omega-3 fatty acids control serotonin synthesis and action, part 2: relevance for ADHD, bipolar disorder, schizophrenia, and impulsive behavior. FASEB J. 2015;29(6):2207-22. PMID: 25713056 | DOI: 10.1096/fj.14-268342

5. Maresz K. Proper calcium use: Vitamin K2 as a promoter of bone and cardiovascular health. Integr Med (Encinitas). 2015;14(1):34-9. PMID: 26770129 | PMCID: PMC4566462