Why does your doctor say you’re low in vitamin D—even though you’ve been taking a multivitamin every day? It’s a frustrating disconnect, but one that actually makes sense when you understand how different vitamins work in the body. Not all nutrients are absorbed, stored, or used in the same way. Some require fat to be properly digested. Others pass through the system quickly if not paired with the right cofactors. And some can be influenced by gut health, stress, or even how much time you spend outside.

Learning the difference between fat-soluble and water-soluble vitamins is one of the most important—and most overlooked—steps in making your supplements truly work for you. Once you know how they behave in the body, you can make better decisions about what to take, how to take it, and why your levels might still be off despite your best efforts.

Fat-Soluble Vitamins: The Long-Term Reserves

Fat-soluble vitamins (A, D, E, and K) dissolve in fat and are stored in your body's fatty tissues and liver. Since they stick around for longer, your body can draw on stored reserves if your daily intake isn’t consistent—but taking too much can lead to buildup and toxicity.

• Vitamin A – Supports vision, immune function, and healthy skin.
• Vitamin D – Helps your body absorb calcium to maintain strong bones, immune function, and mental health.
• Vitamin E – Acts as a powerful antioxidant, protecting cells from damage.
• Vitamin K – Essential for blood clotting and bone health.

Fun Fact: Fat-soluble vitamins rely on dietary fat to be absorbed efficiently. So pairing your supplement or meal with some healthy fat—like olive oil, avocado, or nuts—can help your body make the most of them. 

Water-Soluble Vitamins: The Daily Essentials

Water-soluble vitamins (Vitamin C and B-complex) dissolve in water and aren’t stored in the body, meaning they must be replenished regularly through food or supplements. Any excess is flushed out, so there's less risk of toxicity—but also a greater need for consistent intake.

• Vitamin C – Strengthens the immune system, boosts collagen production, and acts as an antioxidant. 
• B Vitamins (B1, B2, B3, B5, B6, B7, B9, B12) – Support energy production, brain function, and red blood cell formation.

Fun Fact: Those “sky-high” B vitamin percentages on your multivitamin label? They’re not a mistake. Daily values (%DVs) are set to prevent deficiency, not optimize function. In many cases, functional demands are often higher—and your body safely excretes what it doesn’t need for most of the water-soluble vitamins.

Key Differences at a Glance

• Storage: Fat-soluble vitamins stay in the body; water-soluble ones do not.
• Absorption: Fat-soluble vitamins need dietary fat to be absorbed, while water-soluble vitamins are absorbed easily with water.
• Excretion: Excess water-soluble vitamins leave the body through urine, whereas excess fat-soluble vitamins can accumulate.

Finding the Right Balance

Let’s revisit vitamin D. Even though it’s a fat-soluble vitamin that can be stored in the body, it’s still one of the most common nutrient deficiencies—especially during winter months or for anyone who spends most of their time indoors. That’s because vitamin D synthesis depends heavily on sun exposure, and dietary sources alone (like fatty fish, egg yolks, and mushrooms) often aren’t enough to maintain optimal levels. Without regular sunlight or a quality supplement, your reserves can easily run low.

On the other hand, water-soluble vitamins—like vitamin C or the B-complex—need to be replenished daily. They’re used quickly and flushed out just as fast, especially during times of stress, illness, or increased physical demands. That’s why you may notice energy dips, weakened immunity, or skin changes when your intake isn’t consistent.

The key takeaway? Fat-soluble vitamins require proper absorption and occasional top-ups, while water-soluble vitamins call for ongoing, daily nourishment. A nutrient-dense, whole-food diet—rich in colorful vegetables, quality protein, and healthy fats—can support both. And when gaps remain, a thoughtfully formulated multivitamin can help you meet your needs without overdoing it.

If you’re looking for extra support, try Rise—our multivitamin packed with 20 science-backed, bioavailable ingredients designed to fill common nutrient gaps and support your health every day.

Conclusion

Not all vitamins are absorbed or used the same way—and that’s okay. The goal isn’t perfection, it’s informed consistency. By understanding how your body works and making intentional nutrition choices, you can better support your energy, immunity, and long-term health.