Blood Work Series - Vitamin D
Why I Track Blood Work (and Why You Might Want To)
When I work with clients who are making meaningful changes to their health—fat loss, muscle gain, improving energy, fixing digestion, or reversing concerning trends—we run blood work about every six months.
That cadence gives us enough time to see real physiological change, not just day-to-day fluctuations. Once someone transitions into a more sustainable maintenance phase, we typically pull labs once per year, similar to how you’d service a well-running engine rather than constantly taking it apart.
I recently ran my own blood work—and honestly, I wasn’t looking forward to it.
Over the last year I’ve been battling a severe back injury that shut down my normal training routine. Layer on the holidays (which usually means more sweet treats and alcohol), and I fully expected to see that reflected in my labs.
Surprisingly, my results came back much better than expected.
That sparked an idea.
Over the next several weeks, I’m going to share one lab marker per week from my own blood work and break down:
What the test actually measures
What’s considered optimal (not just “in range”)
How behavior influences the result
And what that marker means in real life—how you actually feel day to day
We’re starting with one of the most important and most commonly deficient markers I see:
Vitamin D: The Lowest-Hanging Fruit of Internal Health
What Vitamin D Is (and Why Almost Everyone Is Low)
Vitamin D functions more like a hormone than a traditional vitamin. Your body can synthesize it when your skin is exposed to sunlight—specifically UVB rays.
That sounds straightforward, but in practice almost no one gets enough.
If you:
Live north of roughly Atlanta
Work indoors
Wear sunscreen (which you should)
Experience winter
Or don’t regularly spend time in direct sun
…then you are very likely deficient without supplementation.
This shows up consistently in blood work—even in people eating a very “clean” diet.
The upside is that vitamin D supplementation is safe, inexpensive, and highly effective when dosed appropriately and monitored.
My Vitamin D Result
My 25-hydroxy vitamin D level came back at:
81 ng/mL
That places me right at the top end of the optimal range, which I consider to be 60–80 ng/mL.
Given the lack of training over the past year and the time of year, this was reassuring—and it reinforces something I see often with clients: when a few key behaviors are dialed in, internal health can remain surprisingly resilient.
“Normal” vs. Optimal: Why Reference Ranges Can Be Misleading
Most standard lab reference ranges list vitamin D as “normal” somewhere between 30–100 ng/mL, with many labs flagging deficiency only below ~20 ng/mL.
The problem?
Those reference ranges are based on the general population, and the general population is already quite deficient.
So while a value of 30 ng/mL may be technically “in range,” it is rarely optimal for immune health, tissue quality, bone density, or hormonal function.
This is a theme you’ll see repeatedly throughout this blood-work series:
Normal does not necessarily mean healthy or optimal.
Why Vitamin D Matters (What This Actually Feels Like)
Immune Function (Especially in Winter)
Vitamin D plays a central role in immune regulation. Adequate levels are associated with:
Fewer respiratory infections
Shorter illness duration
Better resilience during periods of stress or poor sleep
In real life, this often feels like getting sick less frequently, especially during the winter months.
Soft Tissue Health (Muscles, Tendons, and “Random Tweaks”)
This is one of the most under-recognized benefits.
Over the years, I’ve worked with several athletes who checked all the usual boxes:
Clean diet
Good hydration
Intelligent training design
Solid warm-ups and recovery
Yet they struggled with chronic muscle pulls and tweaks.
Every one of them had vitamin D levels in the low teens or even single digits.
Once supplementation brought their levels into an optimal range, the issue resolved.
In practical terms, this looks like:
Fewer muscle strains
More durable training
Less of that “my body feels fragile” sensation in the gym
Bone Mineral Density (Especially for Women)
Vitamin D is critical for calcium absorption and bone remodeling. Chronic deficiency can negatively impact bone mineral density, increasing fracture risk over time.
This is especially important for women as they age.
In the real world, this translates to:
Better bone density scores on DEXA scans
Reduced long-term fracture risk
More confidence staying active and lifting heavy things
Hormonal Health
Vitamin D influences several hormonal pathways, including those related to:
Testosterone
Estrogen balance
Thyroid function
Insulin sensitivity
When levels are optimal, people often report better energy, improved recovery, and more stable mood.
How to Supplement Vitamin D (What I Recommend)
For most adults, I recommend a Vitamin D3 + K2 combination.
Why D3?
D3 (cholecalciferol) is the most bioavailable form and reliably raises blood levels. If your levels are measured low by your physician you might get Vitamin D2 (Ergocalciferol), often prescribed in high-dose prescriptions (e.g. 50,000 IU weekly). We find D3 to be a better route for chronic supplementation.
Why K2?
Vitamin K2 helps direct calcium into bones and teeth, rather than allowing it to accumulate in soft tissues or arteries. Think of it as improving calcium handling and long-term safety.
General Dosing Guidelines
Winter: ~10,000 IU per day
Summer: ~5,000 IU per day
👉 Liquid Vit D3 + K2 from Thorne
👉 Capsule Vit D3 + K2 from DFH
When to Re-Test Vitamin D
Vitamin D levels don’t change overnight.
If you adjust your supplementation, you should expect to see meaningful changes in blood levels after approximately 8–12 weeks. That’s typically the earliest window where a follow-up test will accurately reflect your new intake.
This is why we avoid over-testing—and why timing matters.
Want to Follow Along With Your Own Blood Work?
If you want to run your own labs and interpret them alongside this series, you can start here:
👉 Complete Male Blood Panel
👉 Complete Female Blood Panel
Each week, I’ll reference markers included in these panels so you can connect the dots with your own internal health.
A Quick Disclaimer
If you are currently taking prescription medications, have a diagnosed medical condition, or are managing a chronic illness, you should consult with your health coach or healthcare provider before making significant supplementation changes.
Blood work is a powerful tool—but it’s most effective when interpreted in proper context.
Next week: we’ll shift gears and dig into metabolic health—what it really means, how it shows up in blood work, and why it affects energy, fat loss, and long-term health far more than most people realize.