If you think about it, vitamin D is pretty amazing—our skin actually makes it out of light from the sun. In fact, vitamin D is the only vitamin our bodies can synthesize in sufficient quantities just from exposure to energy from our planet’s vital star.

This unique vitamin is essential for all sorts of body functions, especially for helping maintain a strong skeleton. But not just that: Low levels of vitamin D have been linked to everything from depression to cancer, so it’s safe to say that the “sunshine vitamin” is pretty important.

However, most of us just don’t get enough. In the U.S. alone, about 40 percent of people have a vitamin D deficiency. While it is possible to get vitamin D from a handful of foods, the main culprit really is lack of exposure to the sun.

That said, we all know that getting enough sun is not always easy—especially in the winter. And, since too much sun exposure carries other risks, it also isn’t a great idea to just soak up the rays with abandon. Instead, it is absolutely essential to make sure we’re doing everything we can to amp up our vitamin D levels in the healthiest ways possible.

Below, a look at five things to do now to avoid vitamin D deficiency this winter and beyond.

1. Add magnesium

Magnesium is essential for properly metabolizing vitamin D and transporting it in the blood. “Nutrients usually act in a coordinated manner in the body. Intestinal absorption and subsequent metabolism of a particular nutrient, to a certain extent, is dependent on the availability of other nutrients,” a recent report in the National Library of Medicine explains. “Magnesium assists in the activation of vitamin D, which helps regulate calcium and phosphate homeostasis to influence the growth and maintenance of bones.” In other words, a magnesium deficiency can exacerbate a vitamin D deficiency, so be sure you’re getting enough of both.

2. Eat a vitamin D-rich diet

It seems basic, but incorporating foods that have high levels of vitamin D can help if your levels are low. The nutrient is fat-soluble, which means it’s best absorbed when eaten with something like dairy. Fill your plate with foods like salmon and rainbow trout; full-fat dairy like milk and yogurt; and fortified foods like orange juice and cereal (note from Margaux: My favorite is the Purely Elizabeth cereal, which has both fiber and vitamin D while being gluten-free.)

3. Be consistent

If you’re worried about vitamin D deficiency, it may be tempting to go for a high single dose in the form of ampoules of over 100,000 IU. However, that seems to be less effective for maintaining constant blood levels over the long term than simply taking smaller regular doses of around 800 to 2000 IU daily. Mega-doses should instead be reserved for cases of severe deficiency and must be prescribed by a doctor.

4. Take your vitamin D supplement with food

Vitamin D is a fat-soluble vitamin, meaning it dissolves in lipids; That’s why it’s usually offered in oily formulations. To optimize its absorption, it is best to take your supplement with a meal that’s loaded with healthy fats, like avocado, seeds, nuts, mackerel, sardines, and salmon. Some studies also suggest that it is best to take it with your largest meal of the day to maximize its benefits.

4. Add vitamin K

Vitamin D is involved in bone metabolism, notably by increasing the intestinal absorption of calcium and indirectly of phosphorus. Vitamin K, another fat-soluble vitamin, also plays a role in bone health as it promotes the binding of calcium to bone. It also acts in synergy with vitamin D: “Taken together, animal and human studies suggest that optimal concentrations of both vitamin D and vitamin K are beneficial for bone and cardiovascular health as supported by genetic, molecular, cellular, and some human studies,” a scientific review found.

5. Morning exposure

If you’re not a morning person, this might not be for you—but studies show that taking in sunlight first thing in the morning (or before 10 in the morning) will help give your body the vitamin D boost it needs, along with setting your circadian rhythm. Factors you should take into account: The weather, your skin tone, and where you live in relation to the equator. It should also be noted that this isn’t a reason to forgo sunscreen, which is needed to protect from free radicals and prevent skin cancer.

6. Get regular blood tests

The only real way to know if you’re lacking vitamin D? Get a blood test. This will help you get a sense of your baseline, eliminate guesswork, and take best course of action. (For the record, a level of over 30 ng/ml is considered optimal.)