Vitamin D: Why So Many People Are Told They're Low
From office workers in Seoul to family members over 60 — here's why vitamin D comes up so often in checkups, and how I think about it.
Almost everyone in my family had "low" results
When we compared lab reports, vitamin D was the repeat offender — across ages, diets, and lifestyles.
Why deficiency is commonly reported
- Indoor lifestyles — less midday sun exposure
- Sunscreen use — important for skin cancer prevention, reduces vitamin D synthesis
- Latitude and season — winter matters
- Skin pigmentation — affects synthesis efficiency
- Aging — skin produces less vitamin D
- Testing frequency — we simply check more now than decades ago
What vitamin D does
It plays a role in bone health and calcium absorption. Research also explores connections to immune function and mood — but supplementation isn't a universal fix for everything.
How I approach supplementation
- Get tested if your doctor recommends it
- Understand your baseline number
- Use an appropriate dose — more is not always better
- Retest after the period your clinician suggests
Checklist before you buy a mega-dose
- Do I have a confirmed low level?
- What's my target range per my doctor?
- Am I taking other supplements with overlapping risks?
- Do I have conditions affecting fat absorption?
When to involve your doctor
- Kidney disease, hypercalcemia history
- Taking medications that interact with vitamin D
- Pregnancy or pediatric dosing
What I learned
Vitamin D is one of the few supplements where testing can actually guide use. Random mega-dosing without labs is guessing — and fat-soluble vitamins aren't harmless at high levels.
Not medical advice. Dosing should be individualized.
Stay in touch
Wellness articles in your inbox
New health and nutrition notes from Korea — thoughtful, not salesy. Free, unsubscribe anytime.