7 Vitamin D Interactions to Watch For

Vitamin Dplays a significant role in maintaining healthy bones. It also helps regulate your muscular, nervous, and immune systems.

Your body makes vitamin D when you're exposed tosunlight. You also getvitamin D from foodssuch as fatty fish, mushrooms, and vitamin D-fortified milk or cereal. Most people get enough vitamin D, but your healthcare team may check your levels if you're at high risk for vitamin D deficiency. If your vitamin D levels are low, they may recommend a vitamin D supplement. Examples includevitamin D₂(ergocalciferol) andvitamin D₃(cholecalciferol). These supplements are available over the counter (OTC). But some forms and doses of vitamin D are available only by prescription.

Not getting enough vitamin D can lead tovitamin D deficiency. This can cause several health issues, includingosteoporosis(weakened bones). So vitamin D supplements may be important to your overall health. But some medications interact with vitamin D. This increases your risk of side effects.

EXPERT PICKS: WHAT TO READ NEXT

• What's the correct vitamin D supplement dose?Not everyone needs a vitamin D supplement. But if you do, taking theright doseis important.
• What causes Vitamin D deficiency and how do you treat it? There are several causes for vitamin D deficiency, and afew treatment options too.
• Can you get vitamin D through foods?Yes, and here are some of thebest sources.

Here, we'll cover seven vitamin D drug interactions and how to prevent or manage them.

1. Some statins, such as atorvastatin

Statinsare a group of medications that lower cholesterol levels. Some statins are metabolized (broken down) by an enzyme (protein) in your liver called cytochrome P450 3A4 (CYP3A4).

Vitamin D canmake CYP3A4 more active. Because of this, vitamin D may decrease blood levels of certain statins that are metabolized by this enzyme. This can make your statin less effective. Examples of statins that may be affected include:

• Atorvastatin (Lipitor)
• Lovastatin (Altoprev)
• Simvastatin (Zocor)

It's important to note that although an interaction is possible, this doesn't mean you can't take vitamin D and a statin together. And it's not clear how significant this reaction is, even if it does occur. Tell your prescriber if you're taking one of these statins along with vitamin D supplements. They may want to monitor your cholesterol levels more closely. If needed, they may recommend switching to a statin that isn't metabolized by CYP3A4, such as rosuvastatin (Crestor).

2. Bile acid sequestrants, such as cholestyramine

Another group of cholesterol medications is calledbile acid sequestrants. These can also interact with vitamin D. One example of a bile acid sequestrant ischolestyramine(Prevalite).

These medications bind to fat-soluble vitamins like vitamin D in the intestines. This may reduce the amount of vitamin D your body can absorb. So if you're taking a bile acid sequestrant with vitamin D, tell your prescriber. They may recommend separating your vitamin D supplement from your bile acid sequestrant. For example, some experts recommend taking vitamin Dat least 1 hour beforeor 4 hours after your cholestyramine dose.

Alternatively, your prescriber may recommend taking vitamin Donce weekly. This dose is available by prescription only. With a once-weekly dosage, you'll have to space your vitamin D medication from your bile acid sequestrant only 1 day a week (instead of daily).

3. Some antibiotics, such as rifampin and isoniazid

Rifampin (Rimactane) and isoniazid are antibiotics that treattuberculosis. Rifampinincreases CYP3A4 activity, while isoniazidblocks CYP3A4.

Vitamin D can make CYP3A4 more active. But CYP3A4 also helps convert vitamin D to a form that the body can use. So rifampin and isoniazid, which may be used alone or together, canaffect how vitamin D supplementsare metabolized.

If you take medication to treat tuberculosis, tell your healthcare team if you also take vitamin D supplements. They can monitor your vitamin D levels and recommend vitamin D dosage adjustments if needed.

4. Some seizure medications, such as phenytoin

Some seizure medications, including phenobarbital, phenytoin (Dilantin, Phenytek), and carbamazepine (Tegretol), candecrease vitamin D levels. They do this byspeeding up the breakdown of vitamin Din the body. This is why vitamin D supplements may be recommended for people who take certain seizure medications.

But seizure medications can also speed up how quickly vitamin D supplements are broken down. So you may need a higher dose of your vitamin D supplement if you're taking a seizure medication. Ask a healthcare professional what dosage of vitamin D is best for you.

5. Orlistat

Orlistat (Xenical) is a prescription medication used to help withweight loss. It's also available OTC without a prescription (Alli).

Orlistat works by blocking your body from absorbing fat in food. And because vitamin D is a fat-soluble vitamin, orlistat candecrease absorption of this vitamin.

If you take orlistat, taking a vitamin D supplement may be recommended. In fact, it's often recommended to take a multivitamin containing all fat-soluble vitamins (vitamin A, D, E, and K) while you're taking orlistat. It's best to take vitamin D at bedtime orat least 2 hours apart from an Orlistatdose.

6. Digoxin

Digoxin (Lanoxin) is a medication that treats conditions likeheart failureandatrial fibrillation(an abnormal heart rhythm).

Taking digoxin with regular doses of vitamin D supplements doesn't usually cause a vitamin D drug interaction. But high doses of vitamin D mayincrease your blood calcium levels. Having high calcium levels while taking digoxin increases your risk fordigoxin toxicity. This can lead to nausea and vomiting, diarrhea, and heart rhythm problems. In some cases, digoxin toxicity is life-threatening.

If you take digoxin, ask your prescriber before taking vitamin D supplements. They may want to monitor your blood calcium levels more closely and possibly adjust your vitamin D dosage.

7. Thiazide diuretics, such as hydrochlorothiazide

Diuretics, sometimes called water pills, help your body get rid of excess fluid. Diuretics are prescribed for several conditions, including high blood pressure.

Hydrochlorothiazide (Microzide) belongs to a class of diuretics called thiazides. Thiazides help your body get rid of excess water, but they also decrease how much calcium your body gets rid of. As a result, calcium can build up in your bloodstream.

Vitamin D increases calcium absorption. So takingthiazides and vitamin Dcan makehypercalcemia(high calcium levels) more likely. Hypercalcemia can lead to health problems, such as kidney stones and abnormal heart rhythm.

If you're over 65, have existing kidney problems, or havehyperparathyroidism, your risk of developing hypercalcemia is higher. If you take a diuretic, ask your prescriber before taking vitamin D supplements. They'll know if vitamin D is safe to take with your medication.

Frequently asked questions about vitamin D interactions

Can you take vitamin D with blood pressure pills?expand_more Medications used to treat high blood pressure are generally safe to take with vitamin D supplements. Examples include:

• Angiotensin-converting enzyme (ACE) inhibitors, such aslisinopril(Zestril, Qbrelis)
• Angiotensin II receptor blockers(ARBs), such aslosartan(Cozaar)
• Calcium channel blockers, such asamlodipine(Norvasc)
• Beta blockers, such as metoprolol (Toprol XL,Lopressor)

In fact, some research shows that taking vitamin D supplementsmay help lower blood pressurein people with high blood pressureandvitamin D deficiency.

But thiazides can increase your risk of hypercalcemia when taken with vitamin D supplements. Since hydrochlorothiazide is afirst-choice medication for high blood pressure, it's important to let your prescriber know if you take this medication.

Do steroids interact with vitamin D?expand_more

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" data-qa="ContentCalloutH2Title" The bottom line

Vitamin D helps you maintain strong bones and supports your overall health. The best way to get vitamin D is from sun exposure. You can also get it from foods. But if you have low vitamin D levels, a healthcare professional may recommend a vitamin D supplement. Examples includevitamin D₂(ergocalciferol) andvitamin D₃(cholecalciferol).

Some medications can cause drug interactions when taken with vitamin D. This can increase your risk of side effects or prevent your body from absorbing vitamin D. Examples of medications that can interact with vitamin D include atorvastatin (Lipitor), orlistat (Xenical, Alli), and hydrochlorothiazide (Microzide). Other examples include rifampin (Rimactane), phenytoin (Dilantin, Phenytek), and digoxin (Lanoxin).

Give your healthcare team a list of all the medications you take before taking vitamin D. They can check for vitamin D interactions and determine if you need to make changes to your medication regimen.

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