When ‘Acceptable’ Vitamin D Hides Insufficiency: A Physician’s Discovery

We’re both physicians. We both had ‘acceptable’ Vitamin D levels. We were both insufficient.

I’m Sara Szal, an OB/GYN with 30 years of experience. My Vitamin D was 32 ng/mL. My doctor said, “You’re fine. Above 30 is sufficient.”

But I was struggling with recurrent infections, seasonal mood issues every winter, rising anti-nuclear antibodies, and a slowing metabolism. Nobody connected it to my conventionally defined ‘acceptable’ Vitamin D level.

Brad Jacobs is a longevity and concierge physician. His Vitamin D was 35 ng/mL. By conventional standards, he was ‘sufficient.’ But he was dealing with rising fasting glucose, higher post-meal glucose on oral glucose tolerance testing and continuous glucose monitoring, and low-grade inflammation. Standard medicine said he was fine. His body disagreed.

What Medical School Didn’t Teach Us

Medical school taught us that Vitamin D prevents rickets. What it didn’t teach us: Vitamin D is a hormone precursor, not just a vitamin. It regulates over 3,000 genes. Every tissue in your body has Vitamin D receptors. Immune cells require it to function properly. And ‘sufficient’ and ‘optimal’ are not the same thing.

When Vitamin D is optimal (50 to 80 ng/mL), your immune system functions properly, hormones synthesize correctly, mood stabilizes, inflammation stays regulated, and cancer risk decreases. When it’s ‘acceptable’ (30 to 40 ng/mL), you prevent rickets. That’s it. The difference between surviving and thriving.

The Female Factor

For me, ‘acceptable’ Vitamin D meant metabolic chaos. Vitamin D affects estrogen and progesterone production, thyroid hormone conversion, insulin sensitivity, immune regulation, and serotonin synthesis. At 32 ng/mL, I had depression, autoimmune flares, and hormonal disruption. Optimizing to 65 ng/mL changed everything. My body wasn’t failing. My Vitamin D was.

Why Standard Ranges Fail

The ‘normal’ range (30 to 100 ng/mL) is based on preventing bone disease. That’s like saying you have enough water to not die of dehydration, so you’re hydrated. Research shows a different picture:

• Under 20: Deficient
• 20 to 30: Insufficient
• 30 to 40: Prevents rickets, not disease
• 50 to 80: Optimal for health
• Over 100: Risk of toxicity

Your doctor tests for survival. You need optimization.

The Research They Ignore

The data on optimal Vitamin D is debated, but the current guidelines assume you inherited a normal vitamin D receptor (VDR) from your parents. Most of our patients have a genomic issue with their VDR and need higher serum levels for healthy function. Vitamin D has more than 300 jobs in the body that extend beyond bone health. Studies show levels of 50 to 80 ng/mL reduce respiratory infections by 50%, decrease autoimmune disease risk, improve mood and reduce depression, optimize hormone synthesis, and reduce cancer mortality. But conventional medicine still uses rickets prevention standards from 1930. The science has moved on but the guidelines have not.

Why Supplementation Isn’t Enough

Most people take Vitamin D wrong. Common mistakes include taking D without K2 (so calcium goes to arteries instead of bones), taking D without magnesium (so it can’t convert to active form), not testing levels and just guessing at dosage, taking synthetic D2 instead of D3, and never retesting to confirm optimization.

I take 5,000 IU D3 plus K2 plus magnesium daily. My level stays at 65 ng/mL. Tested, not guessed.

What Changed When We Optimized

When I optimized to 65 ng/mL, my autoimmune symptoms stabilized, seasonal depression disappeared, hormonal cycles regulated, and immune resilience transformed.

When Brad optimized to 40-60 ng/mL, his prediabetes improved.

Both of us were ‘sufficient’ by conventional standards. Both of us were insufficient for actual health.

What To Request From Your Doctor

Vitamin D insufficiency masquerades as depression, autoimmunity, frequent infections, hormonal dysregulation, poor recovery, and accelerated aging. Here’s what to request:

• 25-hydroxyvitamin D test (not 1,25-dihydroxyvitamin D)
• Target range of 50 to 80 ng/mL, not just over 30
• D3 plus K2 plus magnesium supplementation protocol
• Retest every 3 to 6 months while optimizing

Vitamin D is a hormone system, not just a bone vitamin. Your symptoms are data. It’s time to optimize function, not just prevent rickets. And you may want to test your genetics related to the vitamin D receptor such as with 3×4 Genetics or IntellxxDNA.

Your ‘acceptable’ labs might be hiding hormone dysfunction that’s been labeled as character weakness.

While the optimal range is still debated and most vitamin D studies are poorly designed, we believe higher levels tend to improve function up to a certain limit, around 80 ng/dL.

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