The 90-Day Metabolic Audit: How to Use CGMs and Bloodwork to Validate Your Supplement Stack

The 90-Day Metabolic Audit: How to Use CGMs and Bloodwork to Validate Your Supplement Stack

You've spent €200 on supplements this month. Omega-3s for inflammation. Magnesium for sleep. Adaptogens for stress. A probiotic someone swore changed their life. But here's the question nobody asks: Are they actually working?

Not theoretically. Not according to the marketing copy. Actually working—in your body, with your genetics, under your specific metabolic conditions.

Most people treat supplements like a faith-based initiative. You take them. You hope for the best. Maybe you feel different after a few weeks, maybe you don't. But "feeling different" isn't data. It's not actionable. And if you're investing in your longevity, you deserve better than guesswork.

This is your 90-day metabolic audit: a systematic protocol for using continuous glucose monitors (CGMs), targeted bloodwork, and symptom tracking to validate whether your supplement stack is moving the needle—or just expensive urine.

Why most people waste money on supplements that don't work for them

The supplement industry operates on a one-size-fits-all model. You read that ashwagandha lowers cortisol in clinical trials, so you buy ashwagandha. What the study doesn't tell you: that trial used 600mg of KSM-66 extract, taken twice daily, in participants with baseline cortisol levels above 15 µg/dL. Your bottle contains 300mg of root powder (not extract), and your cortisol is already at 8 µg/dL.

You're not taking the wrong supplement. You're taking a supplement without context.

Dr. Peter Attia frequently discusses on his podcast that biomarker tracking is the only way to escape the "supplement roulette" trap. You need baseline data, intervention, and follow-up measurement. Anything less is theater.

What is a continuous glucose monitor and why should non-diabetics use one?

A CGM is a small sensor (about the size of a coin) that sits on the back of your arm and measures interstitial glucose levels every 5-15 minutes. Originally designed for Type 1 diabetics, devices like Freestyle Libre and Dexcom G7 are now accessible to metabolically healthy individuals who want real-time feedback on how food, stress, sleep, and supplements affect their glucose regulation.

Why does this matter if you're not diabetic? Because glucose variability—the peaks and crashes throughout the day—is an early warning system for insulin resistance, inflammation, and metabolic dysfunction. Research in Cell Metabolism shows that postprandial glucose spikes (even within "normal" ranges) correlate with cardiovascular risk, cognitive decline, and accelerated aging.

A CGM lets you see patterns invisible to finger-prick testing:

• How does your morning coffee with MCT oil affect glucose compared to black coffee?
• Does that "healthy" smoothie spike you to 9.5 mmol/L for 90 minutes?
• Is your magnesium glycinate actually improving overnight glucose stability?

One user on r/QuantifiedSelf wrote: "I wore a CGM for two weeks and realized my 'clean' oatmeal breakfast spiked me higher than a burger. Changed everything."

What bloodwork markers actually matter for supplement validation?

You don't need a 50-panel test. You need strategic markers that respond to intervention within 90 days. Here's the essential metabolic audit panel:

Glucose Regulation:

• Fasting glucose (target: 4.4-5.0 mmol/L)
• HbA1c (target: <5.3%)
• Fasting insulin (target: <6 µIU/mL)

Inflammation:

• hs-CRP (high-sensitivity C-reactive protein) (target: <1.0 mg/L)
• Homocysteine (target: <8 µmol/L)

Lipid Panel:

• ApoB (apolipoprotein B) (target: <90 mg/dL)
• Triglycerides (target: <100 mg/dL)
• HDL-C (target: >50 mg/dL for women, >40 mg/dL for men)

Hormonal/Thyroid:

• TSH (target: 1.0-2.5 mIU/L)
• Free T3 (if you're targeting metabolic rate)
• Cortisol (morning, target: 10-18 µg/dL)

Nutrient Status:

• Vitamin D (25-hydroxyvitamin D) (target: 40-60 ng/mL)
• Magnesium RBC (red blood cell magnesium, more accurate than serum) (target: 5.0-6.5 mg/dL)
• Omega-3 Index (target: >8%)

Dr. Rhonda Patrick's FoundMyFitness provides detailed breakdowns of optimal ranges versus "normal" lab ranges. Normal is not optimal. Normal is the average of a metabolically sick population.

The 90-Day Protocol: Week-by-Week Implementation

Weeks 1-2: Baseline Data Collection

Before you change anything, you need to know where you stand.

Action Items:

1. Get baseline bloodwork. Schedule with your GP or use a private lab like Medichecks (UK) or Biopredictive (EU). Request the metabolic audit panel above.
2. Apply your CGM. Wear it for 14 days without changing your routine. You're observing, not optimizing yet.
3. Track symptoms daily. Use a simple journal or app (like Bearable) to log:
   • Energy levels (1-10 scale, morning/afternoon/evening)
   • Sleep quality (hours + subjective rating)
   • Digestive comfort
   • Mental clarity
   • Stress/mood

What to Look For:

• Fasting glucose trends (are you waking up at 5.8 mmol/L every morning?)
• Postprandial spikes (which meals send you above 8.0 mmol/L?)
• Glucose variability (are you on a rollercoaster or a steady plateau?)
• Symptom patterns (does brain fog correlate with glucose crashes at 11am?)

One CGM user on YouTube (Levels Health channel) noted: "I thought I had 'low energy genetics.' Turns out I was just crashing from breakfast cereal every single day."

Weeks 3-4: Audit Your Current Supplement Stack

Now that you have baseline data, assess what you're already taking.

Action Items:

1. List every supplement with dosage, form, and timing.
2. Cross-reference with bloodwork. Are you taking Vitamin D but your serum level is still 18 ng/mL? That's a formulation, dosage, or absorption issue.
3. Identify redundancies. Are you taking three different magnesium products because you kept adding without removing?
4. Eliminate variables. Stop everything non-essential for 7 days (a "supplement washout"). Yes, this feels counterintuitive. But you can't validate what's working if you're taking 12 things at once.

What to Expect:

• Some people feel no different (their stack wasn't doing much).
• Some feel worse (they were relying on something effective).
• Some feel better (they were overdosing or reacting poorly to a filler).

Dr. Rhonda Patrick discusses how most people are "supplement hoarders"—they add but never subtract. The washout is uncomfortable but clarifying.

Weeks 5-8: Strategic Re-Introduction (One Variable at a Time)

This is where the audit becomes actionable. You're going to re-introduce supplements one at a time, with 7-10 days between additions.

Action Items:

1. Choose your first intervention. Start with the supplement addressing your biggest deficiency or symptom (e.g., if Vitamin D was 22 ng/mL, start there).
2. Dose correctly. Use evidence-based dosing, not bottle recommendations. For Vitamin D deficiency, that might be 5,000-10,000 IU daily (with K2 for calcium regulation), not 1,000 IU.
3. Monitor glucose response. Some supplements (like berberine or chromium) directly affect glucose. Your CGM will show this within 3-5 days.
4. Track symptoms rigorously. Did sleep improve? Did afternoon energy stabilize? Or nothing?

Example Re-Introduction Sequence:

• Week 5: Vitamin D3 + K2 (10,000 IU + 200 µg MK-7)
• Week 6: Magnesium glycinate (400mg elemental, before bed)
• Week 7: Omega-3 (2-3g EPA+DHA combined)
• Week 8: Metabolic support (e.g., berberine or alpha-lipoic acid if targeting glucose)

What to Look For:

• Fasting glucose dropping by 0.3-0.5 mmol/L (with berberine or magnesium)
• Improved glucose curve smoothness (less variability)
• Symptom resolution (sleep, energy, mood)

Research published in Diabetes Care shows berberine can reduce fasting glucose by 0.6-1.0 mmol/L within 4 weeks—comparable to metformin. If you add berberine and see no change, either your dose is too low, your formulation is poor, or glucose wasn't your primary issue.

Weeks 9-10: Mid-Point Blood Retest

You're halfway through. Time to see if the interventions are translating to biomarker changes.

Action Items:

1. Repeat the metabolic panel. Same lab, same time of day if possible (fasting bloodwork is best done in the morning).
2. Compare to baseline. Has HbA1c dropped? Is hs-CRP lower? Did Vitamin D finally reach 50 ng/mL?
3. Adjust based on results:
   • If Vitamin D is still low, increase dose or switch to a liposomal formulation.
   • If hs-CRP hasn't budged, inflammation might be dietary (not supplement-related).
   • If fasting insulin is still high despite glucose improvements, you may need to extend the protocol or add targeted support.

What Success Looks Like:

• Fasting glucose: 4.4-5.0 mmol/L (down from 5.5-5.8 mmol/L at baseline)
• HbA1c: Dropped by 0.1-0.2% (e.g., from 5.5% to 5.3%)
• hs-CRP: <1.0 mg/L (down from 2.5-3.0 mg/L)
• Vitamin D: 40-60 ng/mL (up from 18-25 ng/mL)

If you're not seeing movement, don't panic. Some markers (like Omega-3 Index) take 90-120 days to shift meaningfully. But fasting glucose and hs-CRP should respond within 6-8 weeks if your interventions are on-target.

Weeks 11-12: Refinement and Long-Term Strategy

You've validated what works. Now you lock it in and eliminate what doesn't.

Action Items:

1. Discontinue non-responders. If you added ashwagandha and cortisol didn't budge, stop taking it. If probiotics didn't affect your digestion, they're not your strain.
2. Optimize timing. Magnesium before bed. Omega-3 with a fat-containing meal. Berberine with your highest-carb meal.
3. Plan your 6-month retest. Metabolic optimization isn't a one-time event. Schedule your next full panel for Month 6 to track long-term trends.
4. Remove the CGM (or cycle it). You've learned what spikes you. Unless you're actively troubleshooting new foods, you don't need 24/7 monitoring. Wear it for 2 weeks every quarter to audit compliance.

What Long-Term Success Looks Like:

• You're taking 4-6 targeted supplements (not 15).
• You understand why you're taking each one (backed by your biomarkers and symptoms).
• You have a retest schedule (every 6-12 months for maintenance).
• You've built metabolic awareness (you know how your body responds to food, stress, sleep disruption).

One r/Biohackers user summarized it perfectly: "I used to spend €300/month on supplements. Now I spend €80 and my labs are better. The CGM taught me that most of my 'supplements' should have been sleep and protein."

How do I interpret glucose spikes on a CGM?

Not all spikes are equal. Context matters.

Normal Post-Meal Response:

• Peak: 7.0-8.5 mmol/L
• Timing: 30-60 minutes after eating
• Return to baseline: Within 2-3 hours

Concerning Response:

• Peak: >9.0 mmol/L (especially if fasting glucose is already elevated)
• Timing: Delayed peak at 90-120 minutes (suggests insulin resistance)
• Prolonged elevation: Still above 7.0 mmol/L at 3+ hours

Dr. Casey Means, founder of Levels, emphasizes that glucose variability matters as much as absolute values. A glucose curve that looks like a mountain range (constant spikes and crashes) drives inflammation even if your HbA1c is "normal."

What if my bloodwork doesn't change but I feel better?

Trust your subjective experience, but verify with more sensitive markers. Standard panels miss nuances.

Consider adding:

• Inflammatory cytokines (IL-6, TNF-alpha) if hs-CRP is stubborn
• Advanced lipid panel (LDL particle number, not just LDL-C) if cardiovascular risk is your focus
• Comprehensive hormone panel (not just TSH, but Free T3, Reverse T3, cortisol awakening response)

Research in Frontiers in Endocrinology shows that subjective improvements in energy and mood often precede measurable biomarker changes by 4-6 weeks. Your body is responding—it just hasn't hit the threshold of detection yet.

Can I do this audit without a CGM?

Yes, but with less precision. Alternatives:

Finger-Prick Testing:

• Test fasting glucose daily (same time each morning)
• Test 1-hour and 2-hour postprandial (after identical meals)
• Track trends over 4 weeks

Limitations: You're getting snapshots, not the full movie. You'll miss overnight glucose patterns, stress-induced spikes, and exercise recovery curves.

Cost Comparison:

• CGM (Freestyle Libre 2): ~€60 for 14 days
• Finger-prick meter + 100 strips: ~€30-40

If budget is tight, use finger-prick testing during Weeks 1-2 and 9-10, and invest in a single CGM cycle during Weeks 5-8 when you're introducing variables.

What about genetic testing—should I include that?

Genetic data (like 23andMe or Nutrition Genome) can inform supplement choices, but it's not essential for the 90-day audit.

Helpful scenarios:

• You have MTHFR variants (methylated B-vitamins become important)
• You're a poor Vitamin D converter (need higher doses or calcifediol instead of cholecalciferol)
• You have APOE4 alleles (omega-3 and antioxidant prioritization for neuroprotection)

But genetics tell you predisposition, not current state. Bloodwork tells you right now. Start with biomarkers. Add genetics later if you hit a plateau.

Final thoughts: Supplements are tools, not magic

The 90-day metabolic audit isn't about proving supplements work universally. It's about proving they work for you, under your conditions, with your biology.

Most people fail at supplementation because they treat it like a religion instead of an experiment. They take something because an influencer said so, or because a study showed a 12% improvement in a population that doesn't resemble them.

You deserve better. You deserve data. And data requires measurement.

If you're serious about longevity, metabolic health, or just not wasting money on snake oil, treat this audit as your initiation. Baseline bloodwork. CGM cycle. Strategic intervention. Retest. Refine.

What you'll discover: most supplements don't move the needle. But the 3-5 that do—when dosed correctly, timed properly, and validated with biomarkers—become non-negotiable.

That's not faith. That's physiology. And it's the only way to build a supplement stack that compounds over decades instead of draining your bank account.

Ready to stop guessing? Start measuring.