How Taking the Wrong Vitamin D Actually Lowers Your Levels

Dr. Joseph Mercola - Take Control of Your Health

Briana Mercola

Health & Fitness, Alternative Health

4.6 • 1.5K Ratings

🗓️ 1 December 2025

⏱️ 8 minutes

🔗️ Recording | iTunes | RSS

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Summary

Taking vitamin D2 instead of D3 can actually lower your body's levels of active vitamin D, leaving you more vulnerable to fatigue, poor immunity, and calcium imbalance
A 2025 meta-analysis confirmed that vitamin D2 triggers faster breakdown of vitamin D3, causing average blood concentrations to drop by about 18 nanomoles per liter
Vitamin D3, the same form your body makes from sunlight, is far more effective at raising and maintaining healthy vitamin D levels than D2, especially in those who are deficient
Regular exercise, even without supplements or weight loss, helps activate and protect stored vitamin D, making it a natural way to sustain healthy levels during winter months
To restore and maintain optimal vitamin D, focus on sunlight exposure, avoid seed oils that make your skin more sensitive to UV damage, and supplement wisely with vitamin D3, balanced with magnesium and vitamin K2

Transcript

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0:00.0	Are you accidentally lowering your vitamin D by taking a supplement that works against you?
0:05.0	Welcome to Dr. Mercola's cellular wisdom. Stay informed with quick, easy-to-listen summaries of our latest articles, perfect for when you're on the go. No reading required.
0:15.0	Subscribe for free at Mercola.com for the latest health insights.
0:19.0	Hello and welcome to Dr. Mercola's cellular wisdom.
0:22.6	I'm Ethan Foster.
0:23.6	Today we're examining why vitamin D2 can drive down your active vitamin D, how
0:28.6	vitamin D3 outperforms it, and the practical steps you can take to restore and maintain healthy levels.
0:35.6	I'm Alara Sky.
0:36.6	You'll hear what a recent meta-analysis found about D2, why D3 aligns with
0:42.1	your biology, how activation inside your cells really works, and how sunlight, smart supplementation
0:49.0	and exercise help you sustain vitamin D all year.
0:53.4	The headline is simple. Taking vitamin D2 can lower your sustain vitamin D all year. The headline is simple.
0:55.0	Taking vitamin D2 can lower your circulating vitamin D3.
0:59.0	A 2025 meta-analysis pooling randomized trials found that people assigned to D2
1:07.0	ended up with about 18 nanomoles per liter, lower D3 than controls.
1:12.6	That pattern held across different ages and durations, which means the drop wasn't noise.
1:17.6	The likely reason is hepatic regulation.
1:20.6	D2 ramps up enzymes that accelerate D3 breakdown.
1:24.6	So the form you actually rely on declines. D3 tells a different story. It's the same form
1:31.7	your skin makes from sunlight, and it's consistently better at raising and maintaining 25
1:36.9	hydroxy vitamin D. Research highlighted in the review noted immune advantages too. D3 supports pathways such as interferon activity that help you recognize and fight infections,
1:49.6	while D2 lacks comparable potency and has, in some contexts, dampened responses.
	...

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