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Nutrient Testing

Understanding vitamin and mineral status—what to test, optimal levels, and how to address deficiencies.

📖 The Story​

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Amanda ate clean, exercised regularly, and took a multivitamin. But she was exhausted, her hair was falling out, and she couldn't shake persistent brain fog.

Her standard labs were "normal." Her doctor suggested stress and prescribed anti-anxiety medication. Amanda knew something was being missed.

She requested nutrient testing beyond the basics. The results were revealing:

  • Vitamin D: 24 ng/mL (insufficient)
  • Vitamin B12: 220 pg/mL (low-normal, but symptomatic)
  • Ferritin: 14 ng/mL (barely normal, often too low for women)
  • RBC Magnesium: Low-normal

Each level was "technically" in range but far from optimal. Combined, they explained everything—fatigue, hair loss, brain fog, anxiety.

With targeted supplementation (not just a multivitamin), Amanda's levels optimized over three months. Her symptoms resolved. The depression and anxiety that were about to be medicated were actually nutrient deficiencies.

"I was eating right but not absorbing right," Amanda realized. "And 'normal' ranges for nutrients are way too broad. I needed to be optimal, not just not-deficient."

The lesson: Nutrient deficiencies are common even with good diet. Testing reveals what food diaries can't—and optimal levels differ significantly from lab "normal."

🚶 The Journey​

The Nutrient Testing Framework

Why Lab "Normal" Falls Short:

NutrientLab RangeOptimalGap
Vitamin D30-100 ng/mL50-80 ng/mL30 is minimum, not goal
B12200-900 pg/mL500-900 pg/mLSymptoms at 200-400
Ferritin15-150 ng/mL (F)50-150 ng/mL15 causes symptoms
RBC Magnesium4.2-6.8 mg/dL5.5-6.8 mg/dLLower half is suboptimal

🧠 The Science​

Understanding Nutrient Markers

Vitamin D​

Why It Matters:

  • Hormone, not just vitamin
  • Affects 200+ genes
  • Immune function, mood, bones, muscles
  • Most people deficient

Testing:

  • 25-OH Vitamin D (standard test)
  • 1,25-OH Vitamin D (active form—rarely needed)
LevelStatus
<20 ng/mLDeficient
20-30 ng/mLInsufficient
30-50 ng/mLAdequate
50-80 ng/mLOptimal
>100 ng/mLMay be excessive

Vitamin B12​

Why It Matters:

  • Nerve function
  • Red blood cell production
  • Energy metabolism
  • Cognitive function

Testing Options:

TestWhat It Shows
Serum B12Total B12 (includes inactive forms)
MMA (Methylmalonic Acid)Functional B12 status (rises when B12 low)
HomocysteineAlso elevated with B12 deficiency

Serum B12 Ranges:

LevelStatus
<200 pg/mLDeficient
200-400 pg/mLLow (often symptomatic)
400-500 pg/mLSuboptimal
500-900 pg/mLOptimal

Note: MMA is more sensitive. If B12 is low-normal but MMA is elevated, functional deficiency exists.

Iron Status​

Why It Matters:

  • Oxygen transport
  • Energy production
  • Thyroid function
  • Cognitive function
  • Hair health

Full Iron Panel:

MarkerWhat It MeasuresOptimal
FerritinIron storage50-150 ng/mL
Serum IronCirculating iron60-170 μg/dL
TIBCBinding capacity250-370 μg/dL
Transferrin Saturation% saturation20-45%

Interpretation:

  • Low ferritin (even in range) → Common cause of fatigue, hair loss
  • Very high ferritin → Inflammation or hemochromatosis
  • Full panel differentiates causes

Magnesium​

Why It Matters:

  • 300+ enzymatic reactions
  • Energy production
  • Nervous system
  • Muscle function
  • Blood sugar regulation
  • Sleep

Testing:

  • Serum Magnesium: Standard but poor marker (only 1% of body mag)
  • RBC Magnesium: Better reflection of cellular status

RBC Magnesium:

LevelStatus
<4.2 mg/dLDeficient
4.2-5.5 mg/dLSuboptimal
5.5-6.8 mg/dLOptimal

Note: Serum magnesium can be normal while body is depleted.

Other Key Nutrients​

Folate:

  • DNA synthesis, methylation
  • Low can cause anemia, neural tube defects
  • RBC folate more accurate than serum
  • Optimal: >400 ng/mL (RBC folate)

Zinc:

  • Immune function, wound healing, testosterone
  • Serum zinc is standard test
  • Optimal: 80-120 μg/dL
  • Competes with copper (don't over-supplement)

Omega-3 Index:

  • Measures EPA+DHA in red blood cell membranes
  • Reflects long-term intake
  • Optimal: 8-12%
  • Most people: 4-5% (suboptimal)

Iodine:

  • Thyroid hormone synthesis
  • Often tested via urine
  • Deficiency common (especially if no dairy, seafood, iodized salt)
  • Don't over-supplement (can worsen autoimmune thyroid)
## 👀 Signs & Signals

Symptoms of Common Deficiencies​

SymptomConsider Testing
Fatigue, low energyFerritin, B12, vitamin D, magnesium
Hair lossFerritin, vitamin D, zinc, thyroid
Brain fogB12, vitamin D, iron, magnesium
DepressionVitamin D, B12, folate, omega-3
AnxietyMagnesium, B vitamins, vitamin D
Muscle cramps/twitchesMagnesium, potassium
Frequent illnessVitamin D, zinc
Poor wound healingZinc, vitamin C
Tingling/numbnessB12
Restless legsIron, ferritin, magnesium

Who's at Risk for Deficiencies?​

PopulationCommon Deficiencies
Vegans/vegetariansB12, iron, zinc
Women of reproductive ageIron
Older adultsB12, vitamin D
People with dark skinVitamin D
Those avoiding sunVitamin D
AthletesMagnesium, zinc, iron
People with gut issuesMultiple (absorption)
Those on certain medicationsVarious (drug-nutrient interactions)

🎯 Practical Application​

Testing and Optimizing Nutrients

Essential Nutrient Panel​

Minimum Testing:

  • Vitamin D (25-OH)
  • Vitamin B12
  • Complete Iron Panel (ferritin, serum iron, TIBC, transferrin saturation)

Comprehensive Panel:

  • Above plus:
  • RBC Magnesium
  • Zinc
  • Folate (RBC)
  • Homocysteine
  • Omega-3 index
  • Vitamin B6 (if indicated)

When to Test:

  • Unexplained fatigue
  • Hair loss
  • Cognitive issues
  • Mood changes
  • Before starting supplementation
  • Monitoring supplementation effectiveness

Preparation:

  • Fasting not usually required for nutrients
  • Note supplements being taken
  • Consider stopping supplements briefly for baseline (discuss with provider)
## 📸 What It Looks Like

Sample Nutrient Panel Interpretation​

Results:

  • Vitamin D: 28 ng/mL (insufficient) ⚠️
  • B12: 320 pg/mL (low-normal, may be symptomatic) ⚠️
  • Ferritin: 22 ng/mL (technically normal but likely causing symptoms) ⚠️
  • RBC Magnesium: 4.8 mg/dL (suboptimal) ⚠️
  • Zinc: 75 μg/dL (low-normal)

Interpretation:

  • All values "in range" but far from optimal
  • This pattern commonly causes fatigue, brain fog, hair loss
  • Combined deficiencies explain symptoms better than individual values

Recommended Supplementation:

  1. Vitamin D3: 5000 IU daily with K2
  2. B12 (methylcobalamin): 1000 μg daily
  3. Iron (bisglycinate): 25-36 mg with vitamin C
  4. Magnesium (glycinate): 400 mg before bed
  5. Retest all in 3 months

Tracking Progress​

NutrientBaseline3 MonthsGoal
Vitamin D285250-80
B12320620500-900
Ferritin226550-150
RBC Magnesium4.85.65.5-6.8
## 🚀 Getting Started

Step 1: Test Your Levels​

  • Request vitamin D, B12, iron panel at minimum
  • Consider RBC magnesium, zinc, folate
  • Get actual numbers (not just "normal")
  • Compare to optimal ranges

Step 2: Identify Deficiencies​

  • Note values below optimal
  • Consider symptoms in context
  • Identify likely contributors (diet, absorption, medications)
  • Prioritize which to address first

Step 3: Supplement Strategically​

  • Choose appropriate forms
  • Start with most deficient nutrients
  • Follow dosing guidelines
  • Take at optimal times (with food, separately from interfering substances)

Step 4: Retest and Adjust​

  • Retest after 3 months
  • Adjust doses based on results
  • Continue or modify supplementation
  • Address absorption issues if levels don't improve
## 🔧 Troubleshooting

Common Nutrient Testing Challenges​

"My levels won't increase despite supplementing"

  • Check absorption (gut health, stomach acid)
  • Consider different form
  • May need higher dose
  • Check for interfering medications
  • Rule out ongoing loss

"I'm not sure which form to take"

  • Vitamin D: D3 (cholecalciferol)
  • B12: Methylcobalamin or hydroxocobalamin
  • Iron: Bisglycinate for gentleness
  • Magnesium: Glycinate for sleep, citrate for constipation
  • Quality matters—choose reputable brands

"I don't know what dose to take"

  • Dose depends on current level
  • Start with conservative dose
  • Test and adjust
  • More isn't always better

"I have multiple deficiencies"

  • Common—they often occur together
  • Address most critical first
  • Can supplement multiple simultaneously
  • Watch for interactions (zinc/copper, iron/zinc)

"Supplements upset my stomach"

  • Take with food (most)
  • Choose gentler forms
  • Split doses
  • Consider liquid or sublingual
  • May indicate gut issues

"My doctor won't test nutrients"

  • Explain symptoms and concerns
  • Direct-to-consumer labs available
  • Find more integrative provider
  • Basic nutrients often covered
## 🤖 For Mo

AI Coach Guidance​

Assessment Questions:

  1. "What nutrients have you tested recently?"
  2. "What symptoms are you experiencing?"
  3. "What's your current diet like?"
  4. "Are you taking any supplements?"
  5. "Do you have any conditions affecting absorption?"

Key Coaching Points:

  • Lab "normal" isn't always optimal
  • Test before supplementing (especially iron)
  • Quality and form matter
  • Symptoms + labs together inform decisions
  • Retest to confirm improvement

Important Boundaries:

  • Cannot diagnose deficiency states
  • Cannot recommend specific doses without test results
  • Encourage working with provider
  • Education about testing and general principles

Example Scenarios:

  1. "My vitamin D is 28—what should I do?":

    • Below optimal (50-80 ng/mL)
    • Typically need 4000-5000 IU D3 daily to raise
    • Take with fat, consider adding K2
    • Retest in 3 months
    • Work with provider for specific dosing

  2. "I'm always tired—what should I test?":

    • Ferritin (iron storage)—common cause in women
    • B12—especially if low-normal
    • Vitamin D—very common deficiency
    • Thyroid if not recently checked
    • These are starting points, not comprehensive

  3. "My B12 is 250—is that okay?":

    • Lab says "normal" but often symptomatic at this level
    • Optimal is 500-900 pg/mL
    • Consider testing MMA for functional status
    • Supplementation likely helpful
    • Especially important if vegan or older
## ❓ Common Questions

Q: Can I test nutrients without a doctor? A: Yes—direct-to-consumer labs offer nutrient panels. However, interpretation and supplementation guidance benefit from working with a provider, especially for complex situations.

Q: How often should I retest nutrients? A: After starting supplementation, retest in 3 months. Once optimized, annual testing is usually sufficient unless symptoms return.

Q: Can I take all my supplements together? A: Some yes, others no. Calcium and iron compete for absorption. Fat-soluble vitamins (D, K) need fat. Magnesium is best at night. Separate iron from most things.

Q: Is it possible to take too much? A: Yes—especially fat-soluble vitamins (A, D, E, K) and minerals like iron. Test before supplementing, don't exceed upper limits without monitoring, and work with a provider.

Q: Do multivitamins work? A: Multivitamins provide baseline coverage but usually insufficient doses to correct deficiencies. Targeted supplementation based on testing is more effective.

Q: Can I get everything from food? A: Ideally, but often not realistically. Modern food is lower in nutrients, many have absorption issues, and vitamin D requires sun exposure. Testing reveals whether diet is sufficient.

## ✅ Quick Reference

Key Nutrient Optimal Ranges​

NutrientLab RangeOptimalTest
Vitamin D30-100 ng/mL50-80 ng/mL25-OH Vitamin D
B12200-900 pg/mL500-900 pg/mLSerum B12 (+ MMA)
Ferritin15-150 ng/mL (F)50-150 ng/mLFerritin
RBC Magnesium4.2-6.8 mg/dL5.5-6.8 mg/dLRBC Magnesium
Zinc60-120 μg/dL80-120 μg/dLSerum Zinc
Folate (RBC)>280 ng/mL>400 ng/mLRBC Folate
Omega-3 Index—8-12%Omega-3 Index

Supplementation Quick Guide​

If LowStart WithRetest
Vitamin D4000-5000 IU D3 + K23 months
B121000 μg methylcobalamin3 months
Ferritin25-36 mg bisglycinate + vit C3 months
Magnesium400 mg glycinate at night3 months

💡 Key Takeaways​

Essential Insights
  1. "Normal" isn't optimal—lab ranges are often too wide
  2. Test before supplementing—especially iron
  3. Deficiencies are common—even with good diet
  4. Form matters—different forms have different absorption and effects
  5. Retest to confirm—make sure supplementation is working
  6. Multiple deficiencies common—they often occur together
  7. Absorption issues exist—if levels don't rise, investigate why
## 📚 Sources
  • Endocrine Society - Vitamin D Guidelines Tier A
  • Institute of Medicine - Nutrient Reference Values Tier A
  • American Society of Hematology - Iron Deficiency Tier A
  • B12 and MMA Research Tier A
  • Omega-3 Index Research Tier A

🔗 Connections​