Quick answer

A multi adds to your nutrient intake from the first dose, but blood levels move more slowly: the main blood marker for vitamin D has a half-life of about 15 days, so a change takes weeks to show. If you already eat well, you may never notice a difference, because a multi fills gaps rather than adding extra.^1,2

Key facts

The body stores about 1 to 5 mg of vitamin B12, roughly 1,000 to 2,000 times a day's intake.³
Serum folate tracks recent intake, while red blood cell folate is a longer-term measure.⁴
Niacin flushing, if it happens, can begin within 30 minutes of a dose.⁵
The longest multivitamin trial ran for a median of 11.2 years.²

What starts with the first dose

The one thing a multi does straight away is add to the vitamins and minerals you take in that day. The claim below is about exactly that, and its grade shows how well it is established.

Helps fill gaps in vitamin and mineral intake when diet falls short*²

Moderate evidence

The NIH Office of Dietary Supplements states that taking a multivitamin and mineral raises nutrient intakes and helps people reach recommended amounts when food alone does not. In a study of 90,771 adults that it cites, about three quarters of men had adequate intakes from food alone and 84% did once a multivitamin was counted. This product supplies 50% or more of the Daily Value for 18 of its 20 listed nutrients; calcium (4%) and magnesium (12%) are token amounts.

Amount studied: One basic multivitamin and mineral a day, with most nutrients close to recommended amounts

Filling a gap is not the same as feeling different. If your diet already covers your needs, there is no gap to fill: the body stores some of the extra, as it does vitamin B12, and passes some out, as it does riboflavin.^3,6

How fast blood levels change

The main blood marker of vitamin D status, 25(OH)D, has a circulating half-life of about 15 days.¹

A half-life of about 15 days means a change in vitamin D intake takes weeks, not days, to show fully in a blood test. A test taken a few days after you start will not show the whole effect.¹

Folate measured in serum reflects recent intake and may not show long-term status, while folate in red blood cells gives a longer-term measure.⁴

So the two folate tests answer different questions: the serum test shows what you have taken in lately, and the red blood cell test shows a longer stretch.⁴

The body stores about 1 to 5 mg of vitamin B12, roughly 1,000 to 2,000 times the amount typically eaten in a day.³

Because the body holds so much B12, NIH notes that a shortfall can take years to show. A store that large is not something a few days of any supplement will visibly shift.³

Will you feel more energetic?

Provides B vitamins that contribute to normal energy-yielding metabolism*^5,7

Moderate evidence

Thiamin, riboflavin, niacin, pantothenic acid, vitamin B6, vitamin B12 and biotin are needed by the enzymes that release energy from food; niacin alone is part of a coenzyme used by more than 400 enzymes. 'Contributes to normal energy-yielding metabolism' is the wording European regulators permit for each of these vitamins, and this product supplies more than the Daily Value of each. It does not mean extra B vitamins give more energy to someone who already gets enough.

Amount studied: The recommended daily intake of each B vitamin, from food and supplements together

The last line of that note is the answer for most people. The job of B vitamins is releasing energy from food, and extra beyond your needs does not add energy. If you feel tired most days, see a doctor rather than waiting for a multi to kick in.⁷

Things some people notice early

Riboflavin, one of the B vitamins, is yellow. The body stores only small amounts, and any excess is either not absorbed or leaves the body in urine.⁶

The other quick change is niacin flushing, described in the safety section below. It is a side effect, not a sign that the multi has started working.⁵

What the long trials measured

The two longest trials tested one formula, Centrum Silver: 14,641 male doctors took it for a median of 11.2 years, and 21,442 older adults for a median of 3.6 years. Trials like these have not shown that a daily multi helps people live longer.²

Results from one multivitamin cannot be applied to others: no two large trials have used the same nutrients in the same amounts.²

Those trials ran for years because the outcomes they tracked, such as how long people lived, take years to measure. They tested one formula, so their timelines cannot be read across to another multi.²

Effects that come on quickly

Niacin in the nicotinic acid form typically causes flushing at 30 to 50 mg or more: the face, arms and chest turn red, with burning, tingling or itching. It can start within 30 minutes and is unpleasant rather than toxic, but it can come with headache, rash, dizziness or a drop in blood pressure. Taking it with food lessens it.⁵

Studies of multivitamin users report no adverse effects except minor stomach and gut complaints, which people taking a placebo had too.²

If flushing comes with dizziness or a rash, or stomach upset keeps happening, stop the multi and talk to your doctor or pharmacist.^2,5

Questions people ask

How long until a multivitamin gives me energy?

It may not. B vitamins help release energy from food, but only someone who was short of them is likely to notice a change, and none of the sources we use puts a time on it.⁷

How long should I take a multivitamin?

There is no set course. NIH notes that no US health agency advises taking one routinely, so whether to keep going depends on whether your diet still has gaps. Ask your doctor if you are unsure.²

See what we make

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Sources

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.