Medically Reviewed

How Long Does It Really Take for Supplements to Work? Experts Explain the Timeline

Vitamins and supplements can support your health in important ways. How long they take to work depends on a variety of factors. Read on to learn more.

There are 13 vitamins that are essential for human health. Nine of them are water-soluble, and four of them are fat-soluble. You can get all of these vital micronutrients from food, but for many reasons, you may not be getting enough of some or many of them.

Dietary supplements are designed to fill the nutritional gaps that may exist in your diet. Some of them may be used to prevent deficiency, while others may be recommended by your doctor to treat a deficiency. The reason that you are taking the vitamin, and many other factors, can influence how quickly you might notice an impact. In this article, we’ll discuss the science of nutrient absorption and how different things affect the way that vitamin supplements might affect how you feel.

Do vitamins start working immediately?

How quickly you notice an impact after starting a vitamin supplement depends on several things. How you (or your medical provider) define whether a nutrient is working can be done in a few ways.

Some vitamins can be measured with laboratory tests. Vitamin D, for example, can be measured with a blood test to help decide if levels are in an adequate range, but the change in your nutrient status may or may not produce physical signs.

Some nutrients are not as easily assessed with lab work. B vitamins are harder to measure with blood tests, at least to determine whether levels are optimal or not. But you might start to feel noticeable differences after you begin taking B vitamins, sometimes within a few days or weeks.

The timeline depends on a few key factors

The differences in how vitamin supplements make you feel usually come down to more than one factor. Let’s discuss them in detail.

Vitamin quality

Vitamin quality refers to the way that a vitamin supplement or product is manufactured. This can include things like supplement purity, manufacturing processes, and the other ingredients that are in a product. When selecting a supplement, check for unnecessary fillers and other important attributes, such as vegetarian or vegan. Care/of utilizes third-party testing to ensure that each product contains the amount of the nutrient that it’s supposed to.

You want to take products that meet and exceed the U.S. Food and Drug Administration cGMP standards, also known as current good manufacturing practices. Third-party testing is an additional way to verify that you’re taking a high-quality product and can feel confident in knowing how much of the nutrient you’re getting each time you take it.

Consistency of regimen

If you’re taking a nutritional supplement, how often you take it will also influence how quickly you may notice its impact. For example, if you follow a vegan diet and want to support healthy B12 intake with a supplement, but you forget to take it a lot of the time, you’re not going to notice the positive impacts of this nutrient. As a water-soluble vitamin, B12 needs to be taken daily to give your body nutritional support. How consistent you are with supplements plays a major role in how they make you feel.

If you have trouble remembering supplements or want some additional support for your wellness routine, use the free Care/of app. In it, you can get activity recommendations to support your health goals. There’s also space to make notes on your progress and how you’re feeling. Plus, you can earn rewards!

Whether you have a deficiency

If you start taking a vitamin to address a nutritional deficiency, there’s a better chance that you will notice results much faster. Obviously, deficiency isn’t an ideal state for anyone, but when it happens, it can lead to a significant impact on quality of life. Doctors may discover nutritional deficiencies accidentally, or they may test you for low levels if you are seen for symptoms that are associated with them.

Some groups of people are more at risk for nutrient deficiencies than others. More than 30% of the U.S. population has been found to be at risk for deficiency in at least one essential vitamin. The most common micronutrient deficiencies include vitamin A, vitamin B6, vitamin B12, folate, iron, vitamin C, vitamin D, and vitamin E.

Common symptoms associated with various nutritional deficiencies can include low energy, poor sleep, digestive disturbances, and changes to the appearance of the skin, eyes, and/or mouth.

If you suspect that you’re deficient in one or more nutrients, see your doctor. Many nutrients can be assessed with a simple blood test.

The vitamin form: water- vs. fat-soluble

There are two classes of vitamins: water-soluble and fat-soluble. This makes a big difference in how they behave in the body.

  • Water-soluble vitamins.) include vitamin C and all of the B vitamins: vitamin B1 (thiamine), vitamin B2 (riboflavin), vitamin B3 (niacin), vitamin B5 (pantothenic acid), vitamin B6 (pyridoxine), folate, and vitamin B12.

  • Fat-soluble vitamins include vitamin A, vitamin D, vitamin E, and vitamin K.

Deficiencies of water-soluble vitamins are typically corrected more quickly than deficiencies of fat-soluble vitamins. This is because the body has no way to store water-soluble vitamins, so it quickly puts to use what you’ve been missing from your diet.

Fat-soluble vitamins often need to be stored and accumulate in your tissue before the body is able to adequately utilize them. This may take weeks or in some cases months.

It’s important to follow your doctor’s or dietitian’s recommendations for nutrient intake to correct a deficiency. More is not always better, and over-consuming some nutrients can lead to toxicity or can disrupt the balance of other important nutrients. Consistency is the most important factor when it comes to using dietary supplements to address nutrient deficiencies.

How the vitamins are stored

Most vitamin supplements can be kept at room temperature, but it’s still important to pay attention to factors that could degrade their quality or effectiveness over time.

  • Don’t store vitamins in the bathroom or other areas that can get humid.
  • Don’t freeze or refrigerate supplements (unless the product explicitly says to).
  • Don’t let vitamins get direct sunlight exposure and don’t leave them in your hot vehicle.
  • Pay attention to manufacturing or expiration dates (over time, vitamins lose their potency).


Vitamins can help you feel your best, especially if you’re addressing a deficiency. But overall, supplements can support your lifestyle–that’s why it’s important to make sure to maintain a healthy one. If you’re eating a balanced diet, supporting healthy digestive function, getting adequate sleep, engaging in regular physical activity, and staying well-hydrated, you’re going to feel better overall, and your supplements will be more effective.

If you’re taking vitamins to support other aspects of your health, it’s important to consider other factors that may reduce how good you’re feeling. Consider the following:

  • Limit alcohol intake.
  • Avoid tobacco use and secondhand smoke exposure.
  • Find healthy ways to manage stress.

Bioavailability and vitamin absorption

There are several things to consider when it comes to bioavailability and how a vitamin absorbs in your body.

Bioavailability refers to how easily your body can activate and use the nutrient. Some supplements come in more than one form. For example, the inactive form of vitamin B6 is known as pyridoxine. In order for your body to use it, it has to be converted or activated into different forms. Because this requires additional steps, and many factors can influence how efficiently the body can do that, some supplement forms of B6 are provided in an already-activated form—either pyridoxal 5' phosphate (PLP) and pyridoxamine 5' phosphate (PMP). Activated nutrients may lead to faster absorption and use by the body. Additionally, taking higher amounts of inactive forms can sometimes cause complications. Lots of inactive B6 can actually prevent active forms of B6 from working in the body, and even with high amounts of inactive B6 in the body, symptoms of deficiency can be present.

Similarly, the forms of vitamin B12 (cobalamin compared to the active methylcobalamin) and folate (folic acid compared to the activated L-5-MTHF or methylfolate) can affect how you may notice the results. Vitamin D3 (cholecalciferol) is also more effective at increasing blood levels compared to vitamin D2 (ergocalciferol).

Each vitamin behaves slightly differently, but the overall principle applies—your body needs forms of vitamins that it can put to use. If a vitamin is in a hard-to-digest form, you will get fewer benefits from it.

Additionally, the concentration of a nutrient can affect how quickly you may notice effects. Many vitamins are referenced on labels as an amount per serving along with a representation of the percentage of the daily value that the supplement provides. A nutrient consumed at a 5% daily value is going to have a dramatically lower impact on your vitamin status than a nutrient that is consumed at a 100% daily value. Many water-soluble vitamins are provided in dietary supplements at higher than 100% daily value because they are not stored in the body.

Finally, the format that the vitamin is consumed in can also affect how well is digested, absorbed, and used. Vitamins typically come in capsules, tablets, chewables, lozenges, liquids, or powders. While the type of product it is won’t always dramatically change how it is used in the body, if you have gastrointestinal conditions, some types may work better than others.

How do you know whether vitamins are working?

There are many ways to determine whether your vitamin supplements are working.

  • For fat-soluble vitamins, like vitamin D, it can take weeks or months, but you can get a simple blood test to check your nutrient status.
  • For water-soluble vitamins, like vitamin B12, a blood test is available, but most doctors will ask you how you’re feeling after a few weeks or a month of taking a supplement to help determine whether it’s working or not.
  • For iron, usually a panel of blood tests is run to determine how your body is both using and storing the nutrient. As a mineral, it behaves differently in the body than vitamins. Similarly to fat-soluble vitamins, it can take some time to show improvements on blood tests, but like water-soluble nutrients, iron supplements tend to make people feel better within days or weeks instead of months. Iron also absorbs better when it’s paired with vitamin C.
  • If you’re supporting your wellness with a multivitamin or a prenatal vitamin, it’s harder to pinpoint a single way of determining that it’s working. This is largely because the point of these is to supply a steady intake of vitamins and minerals over time as a way to reinforce daily nutrient intake from food.

All Care/of formulations have been designed with absorption in mind.

If you’re taking vitamins for a specific reason, work with your healthcare provider to establish how you’ll track progress. This can help you feel confident in your health routine, and will also enable you to let your doctor know if you think something isn’t working as well or as quickly as it should.

Can you speed up the process?

You can’t speed up how quickly a vitamin is absorbed or used in your body. The factors we’ve already discussed explain the variables in timeframes for seeing benefits from vitamin supplements.

What you can control is the rest of your lifestyle, which can have a significant effect on your overall health and how you feel. Small changes, done with consistency, can make a huge difference. If you want to feel better faster, focus on the basics:

  • Eat a nutrient-dense diet that is rich in lots of different vegetables, fruits, healthy fats, protein, and fiber.
  • Get plenty of high-quality sleep by sticking to a healthy sleep routine and practicing good sleep hygiene.
  • Drink enough water each day.
  • Manage your stress as well as you can, try to eat your meals in a relaxed manner and chew your food thoroughly so that your body has an easier time digesting the nutrients.
  • Get regular physical activity and try to make exercise fun (if you enjoy doing something, you’re more likely to stick to it!).

The Bottom Line

Vitamin supplements can go a long way in supporting your health goals and even helping you to feel your best. Because vitamins can absorb differently, and due to several different factors that influence how quickly your body may utilize nutrients, there’s no one-size-fits-all answer as to how fast you’ll notice changes. The most important things to remember are that consistency is important (you can’t get benefits from a supplement you forget to take!) and that all the other elements of your lifestyle help to paint the complete picture of how you’re feeling.

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