10 Herbal Supplement Combinations You Should Never Mix

Published on March 31, 2023

By Lisa Stockwell

Lisa Stockwell

Lisa Stockwell has worked as a copywriter, writer, author, and editor for 35 years, specializing in the field of healthcare since 2009. She recognized the need for reliable health information while supporting friends through unique health challenges and refocused her career to bring clarity and compassion to healthcare communications. Lisa is a graduate of the University of California, Berkeley and a lifelong Northern Californian.

Taking herbal supplements provides a natural way to support your health and vitality. Individual herbs can help address a myriad of health issues — from increasing your energy and boosting your immune system to easing stress and anxiety and improving your digestion and sleep.* 

However, while herbal supplements are generally safe to take individually, some can have adverse interactions when taken together. Certain combinations may also affect your body’s ability to absorb critical nutrients and enjoy the benefits your supplements are meant to provide.

Before you select the best supplements to meet your health needs and goals, it's crucial to understand which combinations to avoid and the best time to take supplements for the healthiest outcomes. 

In this article, we'll explore just a few of the common herbal supplements that should not be mixed together and review tips that will help you maximize your supplements’ effectiveness while minimizing risk. 

Note: This article doesn’t cover all combinations of supplements and medications that may cause issues. Please talk to your medical professional about all supplements and medications.

10 Supplement Combinations to Avoid

As a general rule, before taking any supplement, you should learn about its benefits as well as any potential side effects or adverse interactions it may cause. Gaia Herbs offers an Herb Reference Guide with a thorough profile of every plant used in our herbal supplements. You can learn more about the health benefits of these herbs from our growing library of articles on our Seeds of Knowledge blog. 

There are a limited number of scientific studies on herbs and their chemical compounds. Even fewer studies have been done on the health benefits and risks of herbal combinations. However, we’re aware of several combinations that may be harmful, and you should therefore avoid. We list them below.

Green Tea and Iron

There is nothing unhealthy about either green tea or iron. In fact, iron is an essential mineral that helps your body produce hemoglobin, which red blood cells need to transport oxygen throughout your body, and myoglobin, which provides oxygen to your muscles. 

Green tea is an antioxidant with anti-inflammatory properties that support a strong immune response and reduce oxidative stress, helping to minimize your risk for chronic disease.

But when you take the two together, you limit their effectiveness. 

Iron absorption may be affected by the polyphenols and tannins in tea. Studies have shown that when you consume green tea with an iron supplement or iron-rich meal, it limits the amount of iron your body absorbs.REF#1123 

Since more research is needed to determine how much tea is safe to drink without inhibiting iron absorption, it’s best to drink green tea or take a green tea extract between meals instead of with them — at least an hour before or after the meal. And don’t take an iron supplement with your tea.

Supplements That Thin Blood

Natural blood thinners (anticoagulants) may provide an effective way to reduce your risk of developing blood clots or stroke.* However, taking more than one of these supplements simultaneously (or with another prescribed medication such as Warfarin) could thin your blood too much and increase your risk of bleeding.* Taking natural supplements with medical blood thinners may also limit the effectiveness of the drug. 

Therefore, never use the following supplements in combination without consulting your healthcare provider:

One combination that has been singled out as especially dangerous is Gingko Biloba and Omega 3 fish oil supplements, which may prevent healthy blood clotting and increase your risk of uncontrolled bleeding.

If you have a known medical condition that requires a blood thinner, such as atrial fibrillation, a blood clotting disorder, heart valve replacement, or a knee or hip replacement, don’t take any natural blood thinning supplements — alone or in combination — without the consent of your healthcare provider. 

Supplements with Sedative Effects

Several natural supplements may help with occasional or situational anxiety and promote a better night’s sleep naturally, including*:

In some cases, a combination of herbs may enhance relaxation. Gaia Herbs offers several such combinations our review of the clinical studies suggests are safe and effective when used in combination. It can be dangerous, however, to combine sedative herbal supplements without consulting your healthcare provider for safe dosage recommendations. Taking too much may cause excessive dizziness and sleepiness, alter your mood, and/or impair your ability to think or judge situations effectively.

If you do take an herbal supplement with sedative effects, avoid drinking alcohol at the same time. There are several combinations you should definitely avoid:

  • Valerian and Kava: Taking these supplements together can cause dizziness, confusion, drowsiness, respiratory depression, impaired judgment, and motor control, and difficulty in concentrating.REF#1124 
  • Kava and alcohol: Both Kava and alcohol are natural products that have similar sedative effects and work by depressing the central nervous system. When taken together, they compound these effects. The combination can be dangerous, causing cognitive impairment. While studies are mixed, taking kava together with alcohol may increase your risk of liver toxicity.*
  • St. John’s Wort and Melatonin: St. John’s Wort has been found to increase the beneficial effects as well as the adverse side effects of sedative herbal supplements. It should not be taken with Melatonin (or any other sleep aid) to avoid excess sleepiness.REF#1125
  • St. John’s Wort and Antidepressants: When combined with other antidepressants, St. John’s Wort can lead to a dangerous level of serotonin. Or conversely, it can weaken the effects of the antidepressant. The combination has been known to cause fever, anxiety, elevated heartbeat, muscle spasms, and confusion.REF#1126

Mineral Combinations

Your body needs a balance of minerals to maintain a healthy metabolism and function properly. Ingesting them all at the same time, however, may reduce their absorption. You should get the necessary minerals through a healthy, well-balanced diet. But if you have specific mineral deficiencies and need to take a supplement or two, avoid taking certain combinations at the same time:

  • Vitamin C and Copper: Copper functions with specific proteins as an antioxidant and prevents vascular injury and damage. High dosages of vitamin C have been found to reduce copper absorption.
  • Copper and Zinc: These minerals support immune response and help with wound healing. However, while their relationship is symbiotic, too much zinc can interfere with your body’s absorption of copper and cause a copper deficiency.

To ensure maximum absorption of these mineral supplements, take them at least two hours apart. 

Healthy Tips for Combining Herbal Supplements Safely

Natural plant-based supplements can provide a range of health benefits when you take the right ones for the right reasons at the right time. Here are several tips that can help guide you toward the healthiest choices.

  1. Learn about supplements. Knowledge is power. Many Western Medicine healthcare providers are not well-versed in herbal supplements and what they can do for your health. Educate yourself using our Herb Reference Guide and research-backed literature. 
  2. Always consult your healthcare provider before taking supplements. Discuss your health goals and possible nutrient deficiencies and determine whether the supplements you’ve learned about may benefit your health or interfere with medications you may already be taking. It’s also important for your provider to know what supplements you are taking before prescribing new medications or scheduling surgery.
  3. Ensure that your supplements are of the highest quality possible and sourced from reputable growers. Gaia Herbs offers a Meet Your Herbs guide to provide full transparency and assure you of the purity, integrity, and potency of our products.
  4. Take supplements at the right time of day. When you take supplements can be as important as what supplements you take. Read our article “The Best Time to Take Supplements: How and When to Take Your Herbs,” to get the most out of the herbs you take. 
  5.  Follow the recommended dosages. All reputable supplement providers will list dosage recommendations on their labels. Follow these recommendations unless your healthcare provider directs you otherwise. Do not exceed the recommended dose.
  6. Keep track of side effects. While most herbal supplements have recorded side effects — even minor ones — everybody is unique. You may discover you have an allergy to an herb or react differently than others have in the past. Stop taking the supplement if you experience serious side effects. 

By researching and taking proper precautions, herbal supplements can be a safe and natural way to support your body, providing good health and increased vitality at all stages of life.


  • 1. Salma F Ahmad Fuzi et al,, "A 1-h time interval between a meal containing iron and consumption of tea attenuates the inhibitory effects on iron absorption: a controlled trial in a cohort of healthy UK women using a stable iron isotope", The American Journal of Clinical Nutrition, October 18, 2017.
  • 2. , "Drug Interactions between Kava and Valerian Root",
  • 3. , "Drug Interactions Between Melatonin and St. John's Wort",
  • 4. , "St. John’s Wort", National Center for Complementary and Integrative Health.