Vitamin D: The Sunshine Hormone That Does More Than You Think
- Mohsen Halaby,MD
- Feb 20
- 3 min read
By Mohsen Halaby, MD
Board-Certified in Internal Medicine
Founder, Carebridge Medical
Serving Patients in Ohio & California
Vitamin D is often called the “sunshine vitamin,” but it’s technically a hormone that plays a powerful role in your overall health. From bone strength to immune balance and even metabolic health, vitamin D impacts nearly every system in the body.
At Carebridge Medical, we frequently evaluate vitamin D levels as part of preventive and metabolic health optimization — because deficiency is far more common than most people realize.
What Is Vitamin D?
Vitamin D is a fat-soluble vitamin that your body produces when your skin is exposed to sunlight (UVB rays). It can also be obtained through food and supplements.
There are two main forms:
Vitamin D2 (ergocalciferol) – from plant sources
Vitamin D3 (cholecalciferol) – produced in the skin and found in animal sources (more effective at raising blood levels)
Why Is Vitamin D Important?
1️⃣ Bone Health
Vitamin D helps your body absorb calcium and phosphorus. Without it, bones become weak and fragile.
Deficiency in children → rickets
Deficiency in adults → osteomalacia, osteoporosis
2️⃣ Immune Function
Vitamin D regulates immune responses and helps reduce excessive inflammation. Low levels have been associated with:
Increased risk of respiratory infections
Autoimmune conditions
Slower recovery from illness
3️⃣ Metabolic & Hormonal Health
Emerging research suggests vitamin D plays a role in:
Insulin sensitivity
Glucose metabolism
Weight regulation
Mood stability
Low vitamin D levels are commonly seen in patients with obesity and insulin resistance.
How Do You Know If You’re Deficient?
Many people have no obvious symptoms. Others may experience:
Fatigue
Muscle weakness
Bone pain
Frequent infections
Low mood
A simple blood test — 25-hydroxy vitamin D — measures your level.
General Reference Ranges:
<20 ng/mL → Deficient
20–30 ng/mL → Insufficient
30–50 ng/mL → Optimal for most adults
100 ng/mL → Potential toxicity
Who Is at Risk?
You may be at higher risk if you:
Live in northern climates
Work indoors
Use sunscreen consistently
Have darker skin
Are overweight
Have gut absorption issues
Best Sources of Vitamin D
☀️ Sunlight
10–20 minutes of midday sun exposure (arms and legs) several times per week may be sufficient for some people — depending on skin tone and location.
🥗 Food Sources
Fatty fish (salmon, mackerel, sardines)
Egg yolks
Fortified milk and cereals
💊 Supplements
Vitamin D3 is typically preferred. Common maintenance dosing:
1,000–2,000 IU daily for many adults
Higher doses may be needed if deficient (under medical supervision)
Can You Take Too Much?
Yes — vitamin D is fat-soluble and can accumulate.
Excessive intake may cause:
High calcium levels
Kidney stones
Nausea
Confusion
Always monitor levels if taking high doses.
Vitamin D & Preventive Care
Optimizing vitamin D isn’t just about bones — it’s about:
✔ Supporting immune resilience✔ Improving metabolic health✔ Enhancing overall vitality
At Carebridge Medical, we incorporate vitamin D testing into personalized preventive care and metabolic health plans.
Want to Check Your Vitamin D Level?
If you’re experiencing fatigue, metabolic concerns, or simply want to optimize your health, we can evaluate your levels and guide safe supplementation.
Medical Disclaimer
This blog is for educational purposes only and does not constitute medical advice. Always consult your healthcare provider before starting supplementation
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