Vitamin D Levels: What You Need to Know About Deficiency, Testing, and Fixes

When your body doesn't get enough vitamin D levels, a nutrient critical for bone strength, immune function, and mood regulation. Also known as calciferol, it's not really a vitamin—it's a hormone your skin makes when exposed to sunlight. Most people think they’re getting enough if they drink milk or take a multivitamin, but that’s often not true. Studies show over 40% of adults in the U.S. have levels below what’s considered optimal, even in sunny states.

Low vitamin D deficiency, a condition where blood levels fall below 20 ng/mL doesn’t always cause obvious symptoms. You might feel tired, get sick often, or have achy bones, but many people don’t notice anything until a doctor orders a vitamin D test, a simple blood draw that measures 25-hydroxyvitamin D. The test is cheap, fast, and tells you exactly where you stand. If your level is under 30 ng/mL, you’re likely not getting enough—even if you think you’re doing everything right.

Getting more sun helps, but it’s not that simple. Darker skin, sunscreen use, living north of Atlanta, wearing long sleeves, or staying indoors all cut your body’s ability to make vitamin D. Food sources like fatty fish or fortified milk won’t fix a serious gap either. That’s why most people need vitamin D supplementation, a daily dose of 1,000 to 4,000 IU depending on your level and health. But here’s the catch: taking too much can be dangerous. You can’t overdose from the sun, but pills can build up and cause kidney damage or calcium imbalances.

People with certain conditions—like Crohn’s, celiac, obesity, or kidney disease—are at higher risk. Older adults, pregnant women, and those who avoid the sun entirely need extra attention. Even if you’re healthy, if you’ve never checked your levels, you’re guessing. The best time to test is in early spring, after winter’s long stretch without sun. Results guide what you do next: more sun, a higher dose, or a prescription-strength form.

What you’ll find below isn’t theory—it’s real-world advice from people who’ve been there. Posts cover how medications like proton pump inhibitors can block vitamin D absorption, why some supplements don’t work as claimed, and how to interpret your lab results without a doctor’s lecture. You’ll see what works, what’s a waste, and what to ask your pharmacist when you pick up your bottle. No fluff. Just what you need to get your levels where they should be.