Why Do Vitamins Make Me Tired and Sleepy?

Updated November 8, 2022

Do you take a multivitamin to enhance your daily energy levels? Many people choose to take a daily supplement only to find themselves fighting fatigue on a regular basis. So what's going on? Could your supplement be the cause of your sagging spirits?

Vitamin and mineral deficiencies are known to cause fatigue, so it is natural to expect taking vitamin supplements will boost your energy and improve your overall wellbeing. But this isn't always the case. When taken in high doses, some vitamins and minerals can make you feel tired. Find out which supplements might cause sleepiness when the dose is off.

1. Iron

While iron is an essential mineral, getting too much of it can be toxic. According to the Cleveland Clinic, iron overload (hemochromatosis) is a condition that causes your body to store iron in vital organs, such as your heart, liver and pancreas. When your iron levels are too high, you may notice symptoms such as:

  • Fatigue
  • Irregular heartbeat
  • Joint pain
  • Stomach pain
  • Unexplained weight loss
  • Weakness

To avoid iron overload and the sleepiness or weakness that might come with it, be sure your iron intake is within the recommended dietary allowance (RDA). Men aged 19-50 should get 8 milligrams (mg) per day and women of the same age should get 18mg per day. For men and women over the age of 50, this is 8 mg/day. Avoid taking more than 45 milligrams of iron each day unless recommended by your doctor.

2. Vitamin D

Taking too much vitamin D from supplements can lead to vitamin D toxicity. According to the National Institutes of Health, getting too much vitamin D muscle weakness, confusion, pain, loss of appetite, and other problems. Extremely high levels of vitamin D can even cause death. They add, however, that excessive levels of vitamin D are almost always caused by taking supplements (you can't get too much from sunshine).

To avoid vitamin D toxicity, stay within recommended guidelines. It is recommended that adult men and women get 15 micrograms (mcg) per day and those over age 71 should get 20 mcg.

3. Calcium

Calcium is the most abundant mineral in the body and is good for your bones, teeth, and heart. But too much calcium (hypercalcemia) can lead to weak bones, kidney stones and interfere with your heart and brain health. When hypercalcemia interferes with your brain health, the National Institutes of Health states that it can cause lethargy, fatigue and confusion.

Most Americans get sufficient levels of calcium through consuming calcium-rich foods, such as dairy, leafy greens, and almonds. The RDA of calcium for adults ranges between 1,000 to 1,200 mg daily, depending on your age. Taking more than 2,000 mg a day is not recommended.

4. Vitamin E

Vitamin E toxicity occurs when excessive amounts of vitamin E build up in your body. Vitamin E is a fat-soluble vitamin, which means it is best absorbed when consumed with some fat and is stored in body fat and the liver. According to the Merck Manuals, taking too much vitamin E can increase the risk of bleeding and can cause symptoms such as:

  • Diarrhea
  • Fatigue
  • Nausea
  • Weakness

The best way to get sufficient amounts of vitamin E is through your diet. Foods rich in vitamin E include nuts, seeds, leafy green vegetables and vegetable oils. If you take vitamin E supplements, be sure to keep your intake within the recommended daily amount, which is 15 mg daily for men and women. Women who are breastfeeding need 19 mg daily.

5. Vitamin A

Vitamin A toxicity can occur due to high levels of topical vitamin A or oral vitamin A supplementation. Because vitamin A is fat-soluble and stored in body fat and the liver, it can build up in the body over time and cause toxicity. Vitamin A toxicity can also occur when a large amount is taken over a short period. Vitamin A toxicity symptoms include:

  • Abdominal pain
  • Drowsiness
  • Irritability
  • Nausea
  • Peeling skin
  • Vomiting

Most adults can get sufficient vitamin A through eating a healthy diet. Foods rich in vitamin A include tomato, milk, mango, fish oils, eggs, red bell pepper and leafy green vegetables. The RDA for vitamin A in adults is 700 mcg for women and 900 mcg for men.

6. Vitamin B6

Vitamin B6 is essential for metabolizing carbohydrates, fats, and amino acids. It also supports healthy nerve function, healthy skin, and the formation of red blood cells. Some people may take high doses of vitamin B6 to help manage premenstrual syndrome (PMS) or carpal tunnel syndrome, but there is little scientific evidence that this is beneficial.

Excess vitamin B6 can lead to symptoms such as:

  • Fatigue
  • Heartburn
  • Lack of muscle control
  • Nausea
  • Painful skin lesions

The vitamin B6 RDA is 1.3 to 1.7 milligrams per day for adults. It's important to steer clear of the B6 tolerable upper intake level (100 milligrams per day for adults) to help prevent tiredness.

7. Folate

On its own, excess intake of folate (vitamin B9) isn't linked to fatigue, but taking too much folate can mask a vitamin B12 deficiency. According to the National Institutes of Health (NIH), large amounts of folate may worsen anemia-related fatigue associated with B12 deficiency. Most folic acid supplements are well-tolerated, but oral supplementation may cause:

  • Confusion
  • Irritability
  • Loss of appetite
  • Nausea
  • Sleep pattern disturbance

The daily recommendation for folate intake is 400 mcg for people ages 14 and over. Pregnant and lactating people should aim for 600 mcg per day. The upper limit for folic acid intake is 1,000 mcg daily. If you take a folic acid supplement, you may want to avoid foods and supplements fortified with folid acid to prevent overload.

8. Magnesium

Magnesium toxicity is rare but is more common in the United States than in other countries, most likely due to the wide availability of magnesium supplements. Research shows that magnesium supplements can help regulate sleep patterns and promote a good sleep. Though magnesium is beneficial for reducing insomnia, excessive tiredness is not expected. The NIH suggests calling your doctor immediately if you experience unusual tiredness after taking magnesium oxide.

The recommended dietary allowance of magnesium for adults aged 19 to 51 years is 400-420 mg daily for men and 310-320 mg for women. The upper limit for tolerating magnesium is 350 mg when consumed from supplements only.

When to Call a Doctor

If you're experiencing tiredness that you think may be from a vitamin or mineral supplement, stop taking the supplement and contact your healthcare provider. Fatigue is a common symptom and does not necessarily mean you have taken too much of a vitamin. But if you frequently feel sleepy or tired after taking your vitamin supplement(s), chances are you're taking too much. Your healthcare provider can recommend appropriate doses based on your age, weight, and overall health.

Trending on LoveToKnow
Why Do Vitamins Make Me Tired and Sleepy?