Many people take dietary supplements, such as vitamins and minerals, to fill nutritional gaps in their diet. However, some people may find that taking vitamins can cause issues with getting enough sleep.

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Insomnia is a common sleep disorder affecting 10–30% of adults. People have insomnia when they find it difficult to fall asleep or stay asleep, or they wake up early and cannot go back to sleep.

Research indicates that in 2017–2018, 57.6% of adults in the United States used dietary supplements in the last 30 days. Multivitamins and minerals supplements were the most commonly used dietary supplement.

Some evidence suggests that an inadequate intake of nutrients, such as vitamins A, C, D, E, and K, calcium, and magnesium, links to sleep problems. However, taking supplements of certain vitamins may also lead to sleep disturbances.

In this article, we examine whether vitamins cause insomnia. We also discuss the other possible causes of insomnia and the potential treatment options.

Currently, there is not enough evidence to prove that vitamins cause insomnia. However, some research has identified a link between vitamins and an increase or decrease in a person’s sleep quality.

Deficiencies or higher levels of the following vitamins may impact sleep:

Vitamin D

Growing evidence suggests that vitamin D plays a role in sleep. Studies indicate that vitamin D receptors in several brain areas play a role in sleep regulation. Vitamin D also has involvement in the pathways that regulate melatonin. Melatonin is the hormone that helps control the body’s sleep cycle.

Vitamin D and melatonin have opposite rhythms. The skin synthesizes vitamin D through sunlight exposure, whereas the pineal gland primarily produces melatonin at night.

There is little scientific evidence on how taking vitamin D in the evening affects sleep. However, increasing vitamin D levels with supplements may suppress melatonin generation, leading to sleep disturbances. For this reason, people should take vitamin D supplements in the morning to replicate how the body synthesizes them from sunlight rather than taking them at night.

A vitamin D deficiency may increase the risk of disorders and may have links with sleeping difficulties, shorter sleep duration, and waking up several times.

Vitamin B12

Research shows conflicting findings about vitamin B12’s effect on sleep.

Some research indicates that higher amounts of vitamin B12 link to shorter sleep duration and a higher risk of insomnia. A 2007 study suggests it may also affect the 24-hour biological processes that help a person go from wakefulness through drowsiness to sleep.

However, other research found that elevating vitamin B12 levels did not alter a person’s sleep or waking activities. Furthermore, taking vitamin B complex with magnesium and melatonin may improve sleep regulation and insomnia.

Vitamin C

Vitamin C may affect the duration and quality of sleep. A study comparing short and long sleepers found that people with the lowest vitamin C intake slept for the shortest time. Another study identified high plasma levels of vitamin C among long sleepers.

There was also an association between lower vitamin C intake and nonrestorative sleep, meaning an individual did not feel rested during the day regardless of how many hours of sleep they had.

Researchers are still determining whether taking vitamin C supplements improves sleep. However, some sleep research in cancer patients suggests that increasing vitamin C consumption may benefit sleep health and improve insomnia symptoms.

Vitamin B6

The body needs vitamin B6 for processes involved in metabolism and immune function. It also plays a role in synthesizing many neurotransmitters, including serotonin, which helps regulate sleep patterns.

Older research indicates that deficiencies in vitamin B6 may promote psychological distress, leading to sleep disturbances.

Taking vitamin B6 supplements may improve sleep quality and duration. Research suggests it also enhances the amount of dream content people can recall.

Read more about vitamins and how they work here.

Insomnia can occur as a condition of its own or as a symptom of other conditions.

Causes of insomnia may include:

  • stress
  • disruptions to the internal body clock, due to travel or work commitments
  • poor sleep habits, such as an irregular bedtime schedule
  • unhealthy lifestyle habits, such as stimulating the brain late in the evening by playing video games
  • eating late in the evening
  • mental health conditions, such as anxiety and depression
  • neurodegenerative conditions, such as Alzheimer’s disease
  • neurodevelopmental conditions, such as attention deficit hyperactivity disorder (ADHD)
  • certain medications, such as those for depression, asthma, and high blood pressure
  • sleep-related disorders, such as sleep apnea and restless legs syndrome
  • consuming alcohol, nicotine, and caffeine

Treatment for insomnia will depend on what is causing it. A doctor may recommend a person change their sleep habits, address stress, or treat underlying medical conditions.

If these measures do not improve sleep, a doctor may advise cognitive behavioral therapy (CBT) and over-the-counter (OTC) or prescription sleep medications.

Read more about treatments for insomnia.

Improving sleep habits can sometimes help a person get better sleep. Sleep habits that enhance sleep may include:

  • going to bed and getting up at the same time every day
  • ensuring the bedroom is quiet, dark, and at a comfortable temperature
  • removing electronic devices from the bedroom, such as smartphones, TVs, and computers
  • avoiding large meals, alcoholic beverages, and caffeine before bedtime
  • exercising each day, but not within 3 hours of bedtime

A person should see a doctor if they are consistently tired despite getting enough sleep. Not feeling well-rested could indicate a sleep disorder or other condition.

Researchers need to complete more studies to determine whether or not vitamins cause insomnia. However, some studies suggest having deficiencies or elevated levels of certain vitamins may impact sleep.

Many factors cause insomnia, and insomnia may also be a symptom of another medical condition, such as depression.

Doctors treat insomnia according to the cause and may recommend a combination of lifestyle and sleep habit changes, CBT, and medication.

People should contact a doctor for advice if they regularly have problems sleeping.