does taking vitamins late at night keep you awake?

7 Really Surprising Vitamins That Keep You Awake at Night

(Last Updated On: February 19, 2023)

There are few things worse than not being able to sleep at night. If you’re not sleeping right, dozens of things could be responsible.

Most people don’t realize that vitamin supplements can cause sleepless nights. Since vitamins are essential for your body to function, it sounds counterintuitive.

However, vitamins A, B5, B6, B12, C, D, and K can keep you awake at night. They can also cause side effects like nausea, diarrhea, and muscle cramps.

This happens when you exceed the recommended daily allowance (RDA). Also, vitamins can have undesirable side effects if you take vitamins early in the morning with food.

Why Do Vitamins Keep You Awake?

The most important study was published in the Journal of Sleep Medicine, a medium-scale experiment on hundreds of U.S. citizens to determine whether taking a vitamin or mineral supplement affected sleep time or sleeping patterns.

They found that taking a multivitamin or multiple single vitamins was associated with poor sleep maintenance compared to individuals who didn’t take vitamin supplements because:

  • Vitamin usage causes poor sleep in certain individuals, i.e., due to genetics.
  • Multiple vitamins combine to disturb sleep.
  • People who take vitamins may have done so because they sleep poorly.
  • People with depression or anxiety, which cause poor sleep, may take vitamins to aid their condition.

They were unsure why people taking vitamins sleep worse. However, they may have overlooked the effects on serotonin and melatonin production.

These two chemicals dictate when we feel awake and sleepy. Several vitamins affect the production of these chemicals, but there’s no scientific consensus on the matter.

What Vitamins Cause Sleeplessness?

There are a surprising number of vitamins that cause insomnia. In fact, more vitamins cause insomnia than don’t. However, as mentioned, this can be avoided by taking the right amount.

Ensure you don’t exceed the RDA and take them at the right time.

Let’s look at which vitamins can keep you awake at night:

what vitamins can cause insomnia?

1/ Vitamin A

Vitamin A can keep you awake at night if you take it at the wrong time. Vitamin A, also known as retinol, is one of the vitamins that sets the circadian rhythm.

The circadian rhythm is the 24-hour body clock that regulates, among other things, the time that we sleep. Vitamin A plays an important part in our body clock.

Specifically, vitamin A plays a significant role in optical health and eyesight.

Vitamin A tells the brain that it’s daytime by translating sunlight into a signal to create more serotonin. When it’s late, and less of this signal comes through, the brain creates more melatonin. Without vitamin A, this function is impossible.

However, you can get too much vitamin A, known as chronic hypervitaminosis A. In a study by Rune Blomhoff, one of the symptoms of chronic hypervitaminosis A is sleep disturbance.

It takes a lot of vitamin A to experience adverse symptoms. However, since vitamin A is fat-soluble, your body stores it over time.

Recommended Dosage

The recommended dosage for males aged 19-30 is 900 mcg and 700 mcg for females aged 19-30.

Exceeding this dosage by a small amount could have unwanted side effects because vitamin A can build up in the body over time since it’s stored in the fat.

The dosage is in mcg, not mg- a microgram is one-thousandth of a milligram and one-millionth of a gram. A dollar bill weighs one gram, which is why you can weigh money and know the value.

2/ Vitamin B5

B vitamins include B1, B2, B3, B5, B6, B7, B9, and B12.

Vitamin B5 enables your body to produce serotonin and melatonin. These two chemicals—the first a neurotransmitter and the second a hormone—are responsible for maintaining our natural sleep cycle.

The body produces serotonin in the morning to make you feel more awake and alert. Your body is triggered by sunlight to produce it, so those blind from birth often have delayed sleep phase disorder or DSPD. Melatonin makes you tired, hence why the body produces more melatonin when it’s dark.

Your body needs tryptophan to produce these chemicals. You can’t get tryptophan from dietary sources, so the body must produce it. To do so, you need vitamin B5.

However, your body can produce too much of either chemical in response to ingesting too much vitamin B5. If you ingest too much, you won’t be able to sleep.

When you’re asleep, vitamin B5 can cause vivid dreams and nightmares.

Recommended Dosage

The recommended daily dosage of vitamin B5 is 5 mg for men and women.

3/ Vitamin B6

Vitamin B6 synthesizes dopamine, which is an important neurochemical.

Dopamine makes you happy and alert, which is one way B6 can keep you awake. However, dopamine doesn’t just give you a fleeting feeling of happiness; it’s also important for your mental health.

Aside from assisting normal dopamine function, vitamin B6 helps the body create energy. Without vitamin B6, the body can’t metabolize glucose. The process, known as glycogenolysis, is how the body creates glucose.

When you eat sugars, your body transforms unstable glucose into stable glycogen. That way, it can later access the energy by transforming it into glucose. Without vitamin B6, this process is impossible.

The same applies to how the body accesses energy stored in fat. Vitamin B6 helps you store energy in fat. With more glucose in your system, you’ll feel energized and alert.

Recommended Dosage

Many food manufacturers add vitamin B6 to their foods. This process is called fortifying, and it’s common for vitamins B6 and B12, among others. So, it’s rare for somebody to lack vitamin B6.

Both men and women need 1.3 mg of vitamin B6 per day.

4/ Vitamin B12

Does vitamin b12 keep you awake at night? Indeed, it does. Again, it can keep you awake by making you feel more energized, so B12 (and B complex supplements) should be taken in the morning.

The vitamin B12 found in supplements is produced by bacteria, which are the only natural sources. However, since animals store vitamin B12 in the liver and muscles, you can find it in a meat-rich diet.

Vitamin B12 promotes the healthy function of the nervous system and creates red blood cells. Because of this unique function, B12 helps to prevent anemia, one of the symptoms of which is fatigue. More red blood cells means that your brain has access to more oxygen, making you feel more alert.

There isn’t much scientific evidence about what happens if you ingest too much vitamin B12. Similarly, there’s no research on what happens when you take vitamin B12 too late at night.

That said, anecdotal evidence suggests that B12 can keep you awake. The same people say that it gives them energy and makes them feel more awake.

Recommended Dosage

The recommended dosage of vitamin B12 depends on your health and diet.

Certain diets, especially vegan and vegetarian, are much lower in B12 than others. If so, it’s recommended that you take a vitamin B12 supplement or eat foods fortified with vitamin B12.

Pernicious anemia is possible, making it harder for your body to absorb vitamins like B12.

The recommended amount of vitamin B12 per day is 2.4 mcg for men and women.

5/ Vitamin C

Vitamin C might be one of the vitamins you expect to find in this list. You’ve probably heard that it can keep you more energized, but scientists are divided on whether that’s true.

A study by the International Journal of Sports Medicine found that marathon runners who took vitamin C (versus those that took a placebo) didn’t have extra energy before, during, or after running a marathon.

However, other studies suggest that it makes you feel more awake. Another Nigerian physiological Journal study found that vitamin C reduced stress and fatigue levels in sleep-deprived rats.

While it doesn’t give you any physical energy, it stops you from feeling as tired as you should after sleep deprivation. It also enables the cells to produce physical energy, making you feel more alert.

Taking a large dose of vitamin C before bedtime makes you feel more energized and less like sleeping.

Recommended Dosage

Vitamin C isn’t naturally synthesized in the body, but that doesn’t stop the body from needing lots of it. It’s difficult to ingest too much vitamin C (hypervitaminosis C) because the body flushes out any extra.

Men need 90 mg, and women need around 75 mg of vitamin C per day.

6/ Vitamin D

Vitamin D is a known cause of sleeplessness, but it’s unlikely to be a problem.

Our lifestyles make vitamin D deficiencies a global health problem. It’s so common that a study in the International Journal of Health Sciences called it an epidemic.

Most people don’t need vitamin D supplements because the body produces vitamin D from sunlight.

Due to our lack of vitamin D, taking too much is difficult unless you take more than the RDA through supplements. It has a remarkable effect when your body gets too much vitamin D before bedtime.

It makes your dreams far more vivid and encourages lucid dreaming. This is where you can control your dreams and dream about whatever you want.

Recommended Dosage

The body needs little vitamin D, and it would be impossible to get too much from sun exposure. However, if you take certain supplements with vitamin D, it’s more likely to happen.

Some people are more susceptible to hypervitaminosis D and can develop hypercalcemia.

Both men and women need 15 mcg of vitamin D per day.

Vitamins that cause sleeplessness

7/ Vitamin K

Vitamin K may cause sleepless nights for some but not others.

Without vitamin K, blood clotting would be impossible. A deficiency causes symptoms similar to hemophilia, where cuts or scrapes continue bleeding without clotting.

Vitamin K is formed in leafy, green vegetables, and the body’s bacterial gut flora then converts it into various forms. Few people actively seek vitamin K supplements, but those who do may find that it can cause a stress reaction if you take too much. The reasons for this are unclear.

Anecdotal evidence points to the fact that vitamin K2—one of the several forms of vitamin K—can make you sleepier instead of more alert.

Scientists have only studied vitamin K’s health benefits, not to determine if it keeps a person awake since this is less important. So, you’d need to take vitamin K to discover how it affects you.

Recommended Dosage

You can get enough vitamin K from your diet by eating more vegetables. However, it’s also a common addition to supplements.

Over a normal day, men need 120 mcg, and women need 90 mcg.

Which Vitamins Can You Take at Night?

Vitamins not listed here are fine to take at night, including vitamins B1, B2, B3, B7, and B9.

However, since supplements normally contain all of the B complex vitamins, there’s little point in taking just these five at night and the others in the morning.

It’s far simpler to take a general B complex vitamin early in the day.

Vitamin E

There’s little evidence that vitamin E keeps you awake at night. Rather, it’s a sleep aid that combats restless leg syndrome, enabling people with this condition to sleep better.

Some people claim that it relaxes them and makes it easier to sleep. However, it must be stressed that this evidence is anecdotal, and there’s no research on the effects of vitamin E on sleep.


Much depends on which vitamins are a part of the supplement. If there are a number of the vitamins from the above list—which is likely—they could combine to keep you awake.

The Journal of Sleep Medicine suggested that the various vitamins could interact, exacerbating these effects. However, their study was inconclusive as to whether this was the case.

So, take your supplements in the morning rather than at night. This will help you avoid sleepless nights, but it’s better for you. Your body absorbs supplements better if you take them in the morning because you have them with your breakfast.

Taking supplements on an empty stomach just before bed reduces their efficacy because vitamins and minerals are fat-soluble or water-soluble. Therefore, taking them with a meal dissolves them.