The 7 Best Vitamin D Supplements For Immunity, Bone Health & More In 2025*

Yes. While all nutrients play a crucial, symbiotic role in maintaining health, vitamin D is especially important as this fat-soluble micronutrient is essential for nearly every single bodily system and function including, but not limited to, the musculoskeletal, immune, neurological, thyroid, gastrointestinal, renal, endocrine, and cardiovascular systems.* Since foods deliver very little vitamin D, and relying on sun exposure for everyday vitamin D sufficiency is unreliable (and comes with risks), a high-quality vitamin D supplement is a critical and science-backed approach to achieve and maintain healthy vitamin D levels throughout life.*

Vitamin D3 is the body's preferred form of vitamin D. It has superior bioefficacy, bioactivity, and stability, compared to the other form of vitamin D: vitamin D2. Vitamin D3 also increases serum 25(OH)D levels, your body’s status biomarker, to a greater extent and maintains these higher levels longer than vitamin D2, even though both forms are well absorbed in the gut. D2 is significantly less effective because of the structural differences that affect the way the body metabolizes the vitamin. Vitamin D2 also has increased catabolism (i.e., it's broken down, or metabolized, more quickly) and its metabolites have weaker binding affinity to the vitamin-D-binding protein (i.e., the major vitamin D transport protein that carries the nutrient to the rest of the body to confer all those wonderful health benefits we highlighted before). Overall, if you're looking to increase your vitamin D levels and experience the myriad benefits of sufficient D status, vitamin D3 is the way to go.*

Yes, vitamin D is one of the four essential fat-soluble vitamins our cells, tissues, and entire body requires daily. We need to receive this micronutrient in adequate amounts daily to positively impact vitamin D status (i.e., measured via serum total 25(OH)D) in a meaningful way and thus, reap the myriad of health benefits that come along with it. And while you can receive small amounts of vitamin D from consuming certain foods and variable amounts from UV exposure (i.e., in certain places during certain times of the year), you can’t eat or sun your way to daily vitamin D sufficiency.

Some common signs of vitamin D deficiency can include suboptimal bone health, low mood, less immune resilience, and even brain fog. However, because vitamin D’s role in the body is so ubiquitous, insufficiency may manifest in different ways for different people. The most obvious clue that you have low vitamin D is a low blood test result for serum total 25-hydroxyvitamin D, aka 25(OH)D. Vitamin D insufficiency is a 25(OH)D result of less than 30 ng/mL, while the science and experts indicate a healthy vitamin D blood level is 50 ng/mL or higher.

Many vitamin D supplements feature sub-efficacious doses (i.e., below 5,000 IU), inadequate forms (i.e., vitamin D2 rather than D3), and don't optimize absorption by including fats or encouraging fat consumption (i.e., around a meal) to increase bioavailability. Thus, a vitamin D supplement worth your investment features vitamin D3 (the superior form) instead of D2. In a stand-alone supplement (i.e., not a multivitamin), a good vitamin D supplement will deliver an efficacious dose (5,000 IU for adults) of the vitamin and sometimes even include healthy fats for optimal absorption. Sustainable sources of vitamin D like organic algae earn bonus points.

When you take your vitamin D supplement is really up to you. As long as your supplement contains fat or you consume it around the time of a meal with some fat, you've got plenty of flexibility. To stay consistent, though, try tying your vitamin D supplement to some other part of your routine that happens daily, like drinking your morning coffee or brushing your teeth. If your vitamin D supplement doesn't contain built-in oils for optimal absorption, try tying it to your breakfast (and just make sure you've got some healthy fat like avocado or olive oil in there).* If lunch or dinner works better for your D ritual, go for it!

D3 is the body's preferred form of vitamin D. It's produced in the body naturally and is more efficient at increasing and maintaining healthy blood levels. In fact, compared to vitamin D2, vitamin D3 has superior bioefficacy, bioactivity, and stability. Taking 5,000 IU of vitamin D3 daily paired with a fat (for optimal absorption) is the best option.