Does vitamin D cause constipation?

In this article:

• Vitamin D constipation
• When it might lead to constipation
• How much is too much vitamin D?
• Other causes of constipation
• When to suspect vitamin D
• Tips for taking vitamin D
• The bottom line
• FAQs

In this article

• Vitamin D constipation
• When it might lead to constipation
• How much is too much vitamin D?
• Other causes of constipation
• When to suspect vitamin D
• Tips for taking vitamin D
• The bottom line
• FAQs

Approximately 35% of people in the United States have a vitamin D deficiency, which is both preventable and treatable. Many people turn to vitamin D supplements as the solution because they are convenient, relatively affordable, and easy to take. 

But what happens if you start taking vitamin D and suddenly feel a little … plugged up? Vitamin D can cause constipation, particularly when taken at high dosages. Manage your supplementation and follow a few other simple tips to keep your bowels moving.

Can vitamin D cause constipation?

Vitamin D is great for your immune system, bone health, digestive health, and overall well-being. 

However, vitamin D can cause constipation because it boosts calcium absorption. When there is excessive calcium in your blood, your digestive system slows down and struggles to remove waste. 

When vitamin D might lead to constipation

“Having too little or too much vitamin D3 all at once can cause constipation,” explains Erika Gray, Pharm.D., founder and chief medical officer at ToolBox Genomics.

Too much vitamin D

Vitamin D, the umbrella term for vitamins D2 (ergocalciferol) and D3 (cholecalciferol), helps your body absorb calcium, which is the key electrolyte that your body uses to create muscle contractions and push bowel movements through your system. If you have too much vitamin D, you wind up with too much calcium in your blood, a condition known as hypercalcemia.

Hypercalcemia affects many of your body’s systems, including how your kidneys function, how your brain works, and how your digestive system behaves. Too much calcium slows your digestive tract because your muscles struggle to contract, and your stool doesn’t move. 

For reference, a normal blood calcium level for adults is 8.5 to 10.2 milligrams per deciliter. Constipation typically arises once blood calcium levels hit 12 mg/dL or higher.   

“Additionally, vitamin D3 activation needs magnesium,” says Dr. Erika Gray. “When you take too much vitamin D3, your body will use more magnesium to activate the D3, which pulls water away from your GI tract, leaving hard stool behind. An easy hack is to always take magnesium with your Vitamin D3.”

High levels of calcium also prompt your kidneys to pump out more fluid (i.e., you pee a lot). This can lead to dehydration, which hardens your bowel movements and makes passing them even more difficult.

Hypercalcemia may seem mild at first, but left untreated, it can lead to kidney stones, kidney failure, irregular heart rhythms, dementia, and even coma, which can be fatal. Treatment for hypercalcemia largely depends on the cause, though it often includes IV fluids and diuretics to flush your system.

Too little vitamin D

On the flip side, having low vitamin D levels can cause constipation. One study found that people with chronic functional constipation had low levels of 25-hydroxyvitamin D, the main form of vitamin D that circulates in the blood.

Vitamin D works to strengthen your intestinal barrier, which keeps the items in your gut from the rest of your body. If you don’t have enough vitamin D, you could experience what is known as “leaky gut.” When this happens, your bowels may not move as they should, leading to bloating, abdominal pain, and chronic constipation.

If you suspect you have a vitamin D deficiency, work with your healthcare provider to determine an appropriate supplementation plan.

How much vitamin D is too much vitamin D?

The recommended dosage of vitamin D is as follows:

• Children up to age 12 months: 400 IU/day 
• Ages 1 to 70: 600 IU/day 
• 70 and older: 800 IU/day

You’ll often see supplements and medicines measured in grams or micrograms, which represent the product’s weight. For fat-soluble vitamins A, D, E, and K, dosages are expressed in IU (international units), which measure the vitamin’s effects on the body. For vitamin D, 1 IU is equivalent to 0.025 micrograms (mcg). 

You can take more than the above-listed dosages, but be careful not to take too much.

“The NIH and National Academy of Medicine state that 4,000 IU/day is the upper intake amount of vitamin D for adults,” says Ashley Kitchens, MPH, and registered dietitian at Plant Centered Nutrition. “If you have a vitamin D deficiency, however, your doctor may use a higher or prescription dosage for a short period of time to get your vitamin D level within normal limits.”

Overdosing on vitamin D could lead to constipation as well as kidney stones, vomiting, weight loss, muscle weakness, confusion, heart rhythm issues, and stomach issues. You can avoid vitamin D toxicity by staying within the dosage recommendations.

Other potential causes of constipation

Some of the most common causes of constipation are dehydration, low activity, low fiber intake, medications, and medical conditions.

Dehydration

Dehydration is a common culprit of backed-up bowels. Low liquid consumption has been named a predictor of constipation because if you don’t have enough water in your body, your stool can become too dry and hard, making it difficult to pass. 

A simple solution is to make sure you drink enough water every day. Experts suggest that people assigned female at birth should drink 11.5 cups a day, and those assigned male at birth should drink about 15.5 cups of water a day.

Low activity

You know what your colon loves? Exercise! It may sound a little funny, but it’s true. Strong abdominal muscles help regulate your bowel movements. 

When you exercise, your muscles contract—all your muscles, even those muscles down there. Those contractions increase pressure in your abdomen, pushing stool through your colon. Additionally, exercise increases blood flow, which helps you avoid digestive issues. 

People who exercise are less likely to experience constipation. Therefore, establishing and maintaining a routine that includes regular physical activity could help keep the bowel blues at bay.

Low fiber

Are you getting enough fiber? If you aren’t, you could struggle to move your bowels. Fiber poses a double threat to constipation because it softens stools and adds bulk, making them easier to pass. 

Be advised: Too much or too little fiber can cause constipation. Therefore, just like Goldilocks, you need to figure out how much is “just right.” For every 1,000 calories you eat, you should get about 14 grams of fiber. Most adults on a 2,000-calorie diet should target 28 grams of fiber.

Medications and supplements

Many types of medications and supplements list constipation as a side effect. Opioids,  antacids, antidepressants, sedatives, calcium supplements, iron supplements, and diuretics are just a few products that can lead to gut issues. Many people who are constipated take laxatives, but prolonged use can actually weaken the colon and make it harder to pass stool in the long run.

If you’re on a drug that could cause constipation, ask your healthcare professional what you can do to mitigate the risk. Drinking plenty of water and exercising are often recommended.

Medical conditions

Constipation is an unfortunate side effect of some illnesses. Gastrointestinal problems like irritable bowel syndrome (IBS), neurological disorders like multiple sclerosis, and metabolic disorders are all linked to constipation. Always share any symptoms you have with your healthcare provider before taking medications or supplements to treat constipation. 

When to suspect your vitamin D supplement

It can be difficult to narrow down exactly what is causing your constipation because there are so many factors that can impact your bowels. 

“If your constipation starts within one to two weeks of starting vitamin D3 or taking a significantly higher dosage of it, then it’s possible the constipation is from the vitamin D3,” says Dr. Erika Gray. “Always let your healthcare provider know if you have been constipated for more than three days so they can help you determine the cause of your constipation.”

If you stop or lower your dose of vitamin D and the constipation ceases, then it’s possible the supplement was the cause. 

Practical advice for optimal vitamin D supplementation 

“The best way to obtain vitamin D3 is through sunlight,” advises Dr. Erika Gray. “However, in the winter, or if you live closer to the poles, you may have a harder time making vitamin D3 from the UV light that hits your skin.”

In that case, Dr. Gray offers a few tips for supplementing vitamin D:

• Eat sources of vitamin D like fatty fish (sardines, salmon, and mackerel) 
• Use emulsified or oil drop supplements to improve absorption
• Take vitamin D with magnesium to activate and metabolize it
• Eat a meal with healthy fats along with your supplement for better absorption
• Supplement with vitamin D3 instead of vitamin D2 because it’s better at raising vitamin D levels in the blood

Lastly, avoid excessive vitamin D intake by knowing how much you should consume. Consult your healthcare provider for medical advice if you are planning to use vitamin D as a supplement.

The bottom line

Vitamin D and constipation are linked. Too much or too little vitamin D causes issues in your gut. A vitamin D deficiency weakens your system and makes it harder to pass stool, while too much vitamin D leads to hypercalcemia, which can cause constipation. 

If you supplement with vitamin D, make sure you’re taking the suggested dosage. Talk with your provider about any side effects you may experience. 

Frequently asked questions about vitamin D and constipation

Can I get too much vitamin D from sun exposure?

No, it’s unlikely that you can get too much vitamin D from soaking up the sun. When sunlight hits your bare skin, it triggers D3 production. If your levels are already adequate, your parathyroid glands will slow that production process. Also, if you are older or have darker skin, your body will actually make less vitamin D in response to the sun’s rays.

What are the signs of vitamin D deficiency?

Several common symptoms of vitamin D deficiency include chronic muscle pain and weakness, fatigue, hair loss, mood changes, and frequent illnesses. Children may experience issues in growth patterns and joint deformities.

How long does it take for vitamin D supplements to work?

Experts suggest that it can take two to three months to reach steady levels of vitamin D after starting supplementation.

Should I take vitamin D with food?

Yes, because vitamin D is a fat-soluble vitamin, which means that consuming food with healthy fats will help your body better absorb it. Take your vitamin D supplement with a large meal that has fats like olive oil, nuts, avocados, or fatty fish.