As a pharmacist, I review medication lists regularly. Patients may have a written list of the prescription medications they take including the drug name, doses, and how often they take them. What I don’t see that often is a list that also includes the supplements they take.
“Yeah, but those are just over-the-counter supplements.” is a response I hear often. Once I ask specifically about vitamins and herbal supplements, the list often gets longer. A multivitamin in the morning. Melatonin at bedtime. Or that supplement that helps with mood or energy. Sometimes a patient might know the exact product; other times it is a description of the bottle sitting at home or generally what it is for.
Even though these supplements might not seem significant, I have found that reviewing these supplements along with prescription medications could identify potential interactions that may otherwise go unnoticed.
It is easy to understand why supplements are often left off the list. Supplements are often marketed as safe and natural alternatives to support overall health. Because these supplements can be obtained without a prescription, many people may not consider them as important as their prescription medications. They are readily available in grocery stores and online platforms, which can give the impression that they are less medically significant compared to prescription medications.
However, natural does not always translate to safe or risk free, especially when taken along with other prescription medications. Supplements can have pharmacologic effects that can affect how other medications are absorbed, processed and eliminated by the body. This can increase or decrease the effectiveness of the prescribed medications. The goal is not to avoid supplements but to use them safely. Knowing what combinations deserve a closer look can help prevent medication problems.
This article will review common supplements that interact with prescription medications. It will also explain how they interact and what steps to take to use them safely along with prescription medications.
Eight Interactions to Know About
1. St. John’s Wort + Antidepressants
What is it?
St. John’s Wort is an herbal supplement commonly marketed for mood support and mild depression. It is also known to interact with various antidepressant medications including SSRIs such as sertraline (Zoloft), fluoxetine (Prozac), and escitalopram (Lexapro), and SNRIs such as venlafaxine (Effexor) and duloxetine (Cymbalta).
How does it interact?
St. John’s wort can increase serotonin activity in the brain which is also a common mechanism for some antidepressant prescription medications. The NIH warns that taking St. John’s wort with certain antidepressant medications may lead to increased serotonin-related side effects including a rare but serious condition called serotonin syndrome.
What to do?
- Talk with your prescriber or pharmacist before combining St. John’s wort with certain antidepressants as listed above.
- Do not stop a prescribed antidepressant on your own before consulting with your provider.
2. Ginkgo Biloba + Blood Thinners
What is it?
Ginkgo Biloba is another herbal supplement commonly marketed for memory and cognitive health. It is also known to potentially interact with medications that affect blood clotting including anticoagulants such as warfarin (Coumadin), apixaban (Eliquis), and rivaroxaban (Xarelto), as well as antiplatelet medications such as clopidogrel (Plavix) and aspirin.
How does it interact?
Ginkgo can affect platelet function and interfere with the body’s ability to form blood clots. Anticoagulants and antiplatelets stop clots from forming easily. Ginkgo may increase bleeding risk especially when taken along with other prescription medications. The evidence and significance of the interaction vary depending on the specific medication.
What to do?
- Talk with your healthcare provider or pharmacist before starting ginkgo, especially if you are taking an anticoagulant or antiplatelet medication.
- Do not stop taking any of your prescription medication on your own. Talk to your healthcare provider first.
- Watch for unexplained bruising or bleeding while taking ginkgo. Seek medical attention if you experience uncontrolled bleeding.
3. Calcium + Certain Antibiotics
What is it?
Calcium is the most abundant mineral in the body. It plays an important role in building and maintaining strong bones, supporting normal muscle and heart function as well as nerve signaling. It is found in many foods and sold as a dietary supplement in different formulations.
How does it interact?
Calcium has a well-established absorption interaction with certain antibiotics. Calcium can bind to some medications in the gut making it difficult for the body to absorb them. Because of this, less medication may reach the bloodstream making the medication less effective. Some of these prescription medications that are affected include tetracyclines such as doxycycline and fluoroquinolones such as ciprofloxacin and levofloxacin.
What to do?
Check your medication instructions or ask your pharmacist how long to separate the antibiotic from your supplement. Separating the calcium supplement from your antibiotic will prevent calcium from binding to the medication and decreasing the absorption. The recommended timing can vary based on the specific antibiotic.
4. Red Yeast Rice + Statins
What is it?
Red yeast rice is produced by fermentation of a fungus on rice, usually Monascus purpureus. Some red yeast rice supplements contain monacolin K. This chemical is structurally identical to lovastatin, a prescription statin. This supplement is marketed to help lower blood cholesterol levels, blood glucose levels and blood pressure. Depending on the specific product, the amount of monacolin K in supplements can vary making this interaction variable.
How does it interact?
If you are taking a statin (atorvastatin, simvastatin, pravastatin, rosuvastatin, or any other statin), adding red yeast rice may give you additional statin activity. This can increase the chances of experiencing side effects including muscle pain, liver problems and rarely kidney damage.
What to do?
- If you are already taking a statin medication, do not add red yeast rice to your medication regimen unless your provider has approved it.
- If you are already taking both a statin and red yeast rice, discuss this with your provider. Do not stop your prescribed statin or replace it with red yeast rice.
- Seek medical attention if experiencing significant muscle pain, weakness, dark urine or any other concerning symptoms.
5. Potassium + Blood Pressure Medications
What is it?
Potassium is an essential nutrient that is found in foods and available as a dietary supplement. It is commonly marketed to support muscle and nerve function as well as heart and kidney health.
How does it interact?
Some classes of blood pressure medications decrease the amount of potassium eliminated from the body in the urine. This increases the amount of potassium in the body. These medications include:
- ACE inhibitors, such as lisinopril, enalapril, ramipril, and benazepril.
- ARBs, such as losartan, valsartan, irbesartan, and olmesartan.
- Potassium-sparing diuretics, such as spironolactone, eplerenone, amiloride, and triamterene.
Taking potassium supplements along with these medications may result in increased levels of potassium in the body, especially in people with kidney problems. High levels of potassium in the body can interfere with the heart’s electrical activity leading to irregular heart rhythms that can potentially be life-threatening.
What to do?
- Potassium supplements can sometimes be taken along with blood pressure medications but caution is needed. Do not start a potassium supplement if you are already taking an ACE inhibitor, ARB, or potassium-sparing diuretic without discussing it with your provider or pharmacist.
- If you are already taking a potassium supplement, let your provider know. Your provider may monitor your blood potassium levels and make adjustments if needed.
- Be aware that multivitamins and other supplements may also contain additional potassium. Keep a comprehensive list of your medications and supplements and have your pharmacist review it. This will help prevent excessive potassium intake.
6. Ginseng + Warfarin
What is it?
Ginseng is a supplement extracted from the roots of plants in the Panax genus. It is marketed for improved mental focus, stress, anxiety, diabetes, and other conditions.
How does it interact?
Ginseng may affect how well warfarin works. In one study, people taking American ginseng had decreased INR suggesting that ginseng may reduce the anticoagulation effects of warfarin. Reduced INR levels below desired goal range can result in formation of clots. Studies on the effect of Asian ginseng on anticoagulation have mixed results.
What to do?
- If you take warfarin, talk with your healthcare provider or pharmacist before stopping or starting ginseng.
- Do not modify your warfarin doses based on your supplement use. Your provider can make recommendations based on your INR levels.
7. Metformin + Vitamin B12
What is it?
Metformin is a commonly prescribed diabetes medication. Vitamin B12 is an essential water-soluble vitamin that is mainly obtained from animal-based foods. It supports healthy red blood cells and nerve function.
How does it interact?
Evidence supports that long term use of metformin can reduce vitamin B12 levels and sometimes lead to vitamin B12 deficiency. Low levels of vitamin B12 can cause fatigue, anemia and other nerve related symptoms like numbness and tingling.
What to do?
- If you take metformin long term, discuss with your prescribing provider if your vitamin B12 level should be checked periodically. Your provider might recommend a vitamin B12 supplement if your level is low.
- Be aware of symptoms such as fatigue, numbness, or tingling and report them to your healthcare provider. Do not stop taking metformin unless directed to do so by your provider.
8. Iron + Thyroid Medications and Antibiotics
What is it?
Iron is an essential mineral that our body utilizes to make hemoglobin. Hemoglobin is the protein in red blood cells that carries oxygen throughout the body. Iron supplements are commonly used to prevent or treat iron deficiency.
How does it interact?
Iron can bind to certain medications in the digestive tract making it harder for the body to absorb the medications. Taking iron too close to levothyroxine can reduce absorption and potentially make the thyroid medication less effective.
Iron can also bind to certain antibiotics like tetracyclines such as doxycycline and fluoroquinolones such as ciprofloxacin and levofloxacin, which might result in less of the drug in the body.
What to do?
- If you are on levothyroxine, take it first thing in the morning and wait 4 hours before taking iron containing supplements.
- If you are on the antibiotics listed above, check your medication instructions or ask your pharmacist how long to separate the antibiotic from your supplement. Spacing recommendations can vary based on the specific antibiotic.
Can I Just Take Them at Different Times?
Supplements can interact with prescription medications in various ways. Some interactions can easily be managed by changing when you take them. This is especially true for supplements containing minerals like calcium, magnesium or iron. These minerals bind to some medications in the gut and reduce how much medication is absorbed. Spacing the timing of when the supplement is taken can prevent interaction. But one thing to note is that there is no single-spacing rule for every combination. Depending on the way the body absorbs the medication, the timing of the interaction can vary. Check with your pharmacist for specific timing instructions.
On the other hand, some supplements can add to or alter the effects of the prescription medications. In this type of situation, simply taking the supplement and the medication at different times may not prevent the interaction. Talk to your pharmacist or healthcare provider to determine if it is safe to take the supplement with your medication or if additional monitoring is needed.
Tips From a Pharmacist
Keeping track of all the medications you take is hard. Especially if supplements are included. Take time to write down the medications and supplements you take along with the drug name, dose and how often you take it. No supplement or over the counter medication is insignificant to include on your list. If you take it, put it on that list. I have found that most patients prefer to take pictures of the bottles and save them under a photo folder on their phones. Whatever method works for you, keep the information where you can easily access it.
Pharmacists are medication experts and one of the most accessible members of the health care team often without an appointment. Ask your local pharmacist to review your medication list and perform an interaction check of all your prescriptions and supplements. They can help identify any interactions that would increase side effects or reduce the effectiveness of the medications you are taking. Your pharmacist can explain these interactions and provide the next steps. Do not stop taking any of your prescription medications without discussing it with your provider.
This article covers common supplements that can interact with prescription medications, but is not by any means a comprehensive list. Many other supplements could interact with medications. The significance of these interactions depends on multiple factors including your medical conditions and the doses of the medications you take. Having a list of the medications and supplements you take and getting a personalized medication review with a pharmacist is important.
Selam Melka, PharmD, is a pharmacist with more than ten years of experience in clinical pharmacy and acute care. Her work centers on medication therapy evaluation, medication reconciliation and management, and drug information analysis — the everyday work of catching what a long medication list can hide. She collaborates closely with physicians, nurses, and the rest of the care team, and much of her time goes to medication safety education. She writes with one aim: helping readers use their medications safely and effectively.
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