Vitamin D: What It Does, Why You Need It, and How to Get Enough

When we talk about vitamin D, a fat-soluble nutrient your body makes when skin is exposed to sunlight. Also known as the sunshine vitamin, it’s not just a supplement—it’s a hormone that talks to nearly every cell in your body. Most people think it’s only for strong bones, but that’s just the start. Without enough vitamin D, your immune system struggles, your muscles weaken, and your risk for chronic conditions like diabetes and high blood pressure goes up. Even mild deficiency can leave you feeling tired, achy, or down for no clear reason.

Where do you get it? Sunlight is the best source—just 10 to 15 minutes on your arms and face a few times a week can do the trick for many. But if you live in Canada, work indoors, wear sunscreen daily, or have darker skin, your body might not make enough. That’s where food and supplements come in. Fatty fish like salmon and fortified milk help, but they rarely give you enough on their own. That’s why so many Canadians end up needing a daily vitamin D pill, especially in winter. And here’s the catch: you can’t overdose from sunlight, but too much from supplements can cause problems. That’s why knowing your level matters.

Vitamin D deficiency, a common condition marked by low blood levels of the nutrient. Also known as hypovitaminosis D, it’s often silent until you start feeling the effects—fatigue, bone pain, frequent infections. Testing is simple: a basic blood test your doctor can order. And if you’re on long-term medications like steroids or antiseizure drugs, you’re at higher risk. Even people with liver or kidney disease have trouble activating vitamin D, which means their bodies can’t use what they get. Then there’s vitamin D supplements, the most common way to fix a shortfall. Also known as cholecalciferol (D3) or ergocalciferol (D2), they come in pills, drops, or even injections. But not all supplements are equal—some brands are poorly made, and doses can be way off. That’s why knowing what you’re taking, and why, matters more than just grabbing the cheapest bottle. And vitamin D sources, everything from sunlight to fortified cereals. Also known as natural vs. synthetic vitamin D, they vary in how well your body absorbs them. Fatty fish, egg yolks, and mushrooms exposed to UV light are the best food options, but they’re not enough for most people in northern climates.

You’ll find posts here that dig into how vitamin D connects to everything from skin conditions like psoriasis to how your body handles other meds. One article shows how topical vitamin D helps manage severe psoriasis flare-ups. Another explains why people on certain drugs need extra vitamin D just to stay healthy. There’s even a guide on checking your medicine cabinet for expired pills—because if your vitamin D bottle’s been sitting there since 2020, it might not be doing you any good. This isn’t just about taking a pill. It’s about understanding how your body uses it, when you really need it, and how to avoid the traps most people fall into.