Is There a Downside to Taking CoQ10? A Comprehensive Look at the Risks

October 7, 2025 •

4 min read

The global market for CoQ10 supplements was valued at over $621 million in 2023 and is projected to grow, but many users wonder: is there a downside to taking CoQ10? This popular antioxidant, while beneficial for many, is not without potential risks.

Quick Summary

Coenzyme Q10 is generally considered safe, but potential downsides exist. These include mild side effects like digestive upset and insomnia, and significant drug interactions with blood thinners like warfarin and some blood pressure medications.

Key Points

Generally Safe: CoQ10 is considered safe for most adults, with serious side effects being rare.
Mild Side Effects: The most common downsides are mild digestive issues like nausea and stomach pain, and sometimes insomnia with certain amounts.
Drug Interactions: A significant downside is its interaction with blood thinners like warfarin, blood pressure medications, and insulin.
Special Populations: Pregnant or breastfeeding women and children should avoid CoQ10 due to a lack of safety data.
Consult a Doctor: Before starting CoQ10, it's crucial to speak with a healthcare provider to avoid potential risks and interactions.
Two Forms Exist: Supplements come as ubiquinone (more stable, less expensive) and ubiquinol (more bioavailable, often for older adults).
Intake Matters: The appropriate intake can vary; higher amounts may increase the risk of side effects like insomnia.

What is Coenzyme Q10?

Coenzyme Q10 (CoQ10) is a vitamin-like compound that exists naturally in every cell of the human body. Its highest concentrations are found in organs with high energy requirements, such as the heart, liver, and kidneys. CoQ10 plays a crucial role in the production of adenosine triphosphate (ATP), the primary energy source for cells. It also functions as a powerful antioxidant, protecting cells from damage caused by harmful molecules called free radicals. The body produces CoQ10, but its levels tend to decline with age and may be lower in people with certain health conditions like heart disease or those taking statin medications. Because of this, CoQ10 is a popular over-the-counter dietary supplement available in capsules, tablets, and liquids.

The Widely-Touted Benefits of CoQ10

Many people take CoQ10 to address a decline in natural production or to support overall health. Research has explored its potential benefits for various conditions:

Heart Health: Studies suggest CoQ10 may improve symptoms of congestive heart failure, help lower blood pressure, and potentially reduce the risk of repeat heart attacks. The 2022 ACC/AHA/HFSA guidelines noted that CoQ10 supplementation was effective in reducing mortality and hospital stays for heart failure over two years.
Statin-Related Muscle Symptoms: Statin medications, used to lower cholesterol, can also decrease the body's CoQ10 levels. Some research indicates that CoQ10 supplements might help ease the muscle pain and weakness (myopathy) that can be a side effect of statin use.
Migraine Prevention: Some studies suggest that regular supplementation with CoQ10 may reduce the frequency and duration of migraine headaches. One trial found a significant reduction in headache frequency after three months of therapy.
Fertility: As an antioxidant, CoQ10 may protect eggs and sperm from oxidative damage. Some studies suggest it can improve sperm quality and may help improve pregnancy rates in those undergoing assistive reproductive technologies.
General Energy and Fatigue: Given its central role in cellular energy production, CoQ10 has been studied for its potential to reduce fatigue. A 2022 meta-analysis found that CoQ10 supplementation significantly reduced fatigue scores compared to a placebo.

Is There a Downside to Taking CoQ10? A Closer Look at Risks

Despite its benefits and general safety profile, CoQ10 is not entirely without downsides. The risks are generally mild, but some can be significant, particularly concerning drug interactions and specific populations.

Common and Rare Side Effects

Serious side effects from CoQ10 are not known, and adverse effects are uncommon, occurring in less than 1% of users in one study. When they do occur, they are typically mild.

Most Common (Gastrointestinal Issues): The most frequently reported side effects involve digestive discomfort, such as upper stomach pain, nausea, loss of appetite, heartburn, and diarrhea. These issues can often be minimized by taking CoQ10 with food.
Other Mild Side Effects: Some individuals may experience insomnia (especially with certain amounts), headaches, dizziness, fatigue, irritability, or skin rashes.
Liver Enzymes: Very high amounts have been linked in some older research to elevated liver enzymes, which can be a sign of liver stress. However, there is no conclusive evidence that CoQ10 harms the liver, and some recent studies suggest it may even improve liver function in certain conditions.

Significant Drug Interactions

One of the most critical downsides of CoQ10 involves its potential to interact with prescription medications. It is essential to consult a healthcare provider before taking CoQ10 if you are on any other drugs.

Blood Thinners: CoQ10 may decrease the effectiveness of the anticoagulant warfarin (Jantoven), which could increase the risk of a blood clot. This is a significant interaction that requires medical supervision.
Blood Pressure Medications: Because CoQ10 may lower blood pressure, taking it alongside antihypertensive drugs could cause an additive effect, potentially lowering blood pressure too much.
Insulin and Diabetes Medications: The supplement may improve insulin sensitivity and affect blood sugar levels, potentially altering the required amount of insulin or other diabetes drugs.
Chemotherapy: CoQ10 may interfere with some chemotherapy and radiation treatments.

Populations That Should Exercise Caution

Certain groups are advised to avoid CoQ10 or use it only with a doctor's approval due to a lack of safety data or specific risks.

Pregnancy and Breastfeeding: The safety of CoQ10 during pregnancy and lactation has not been established, so its use is not recommended.
Children: CoQ10 should not be given to children under 18 unless directed by a pediatrician.
Individuals with Liver or Kidney Problems: People with liver issues or biliary obstruction should be cautious, as the body eliminates CoQ10 through bile. Similarly, its use in patients with renal impairment is not well-studied.

Ubiquinone vs. Ubiquinol: A Comparison

CoQ10 supplements come in two main forms: ubiquinone and ubiquinol. The body can convert between these two forms.


Feature	Ubiquinone	Ubiquinol
Form	The oxidized form of CoQ10.	The reduced, active antioxidant form of CoQ10.
Bioavailability	Must be converted by the body into ubiquinol; absorption can be less efficient.	Considered to have higher bioavailability as it's already in the active form.
Best For	Younger, healthy individuals and those looking for a more affordable option.	Often recommended for older adults (over 40-50) or those with conditions affecting conversion.
Stability	More stable in supplement manufacturing.	Less stable and may require special encapsulation to prevent oxidation.
Cost	Generally less expensive.	Typically more expensive.

For more information on supplement quality, consider resources like the U.S. Pharmacopeia (USP).

Conclusion

So, is there a downside to taking CoQ10? Yes, but for most healthy adults, the risks are low and the side effects are mild and infrequent. The primary downsides are manageable gastrointestinal upset and, more critically, potential interactions with medications like warfarin and blood pressure drugs. While CoQ10 offers a range of potential benefits, especially for heart health, statin side effects, and migraines, it is not a risk-free supplement. The decision to take CoQ10 should always be made in consultation with a healthcare professional who can assess your individual health status, current medications, and determine the appropriate form and intake for your needs.

Frequently Asked Questions

The most common negative side effects are mild and typically involve the digestive system, such as upper stomach pain, nausea, loss of appetite, and diarrhea. Some people may also experience insomnia, especially with certain amounts.

Yes, a significant downside of CoQ10 is its potential to interact with certain medications. It can reduce the effectiveness of blood thinners like warfarin, potentially increasing clot risk. It can also have an additive effect with blood pressure drugs and may interfere with insulin and some chemotherapy treatments.

People who are pregnant, breastfeeding, or taking blood thinners (like warfarin), certain chemotherapy drugs, or insulin should not take CoQ10 without consulting a doctor. Its safety has not been established in these groups.

Yes, CoQ10 is generally well-tolerated for daily use, even with higher amounts. You should only use it as directed and after consulting with a healthcare provider.

CoQ10 itself does not cause blood clots, but it can increase the risk of a clot if you are taking a blood-thinning medication like warfarin. It does this by potentially making the medication less effective.

Yes. Ubiquinone is the oxidized form of CoQ10 that the body must convert, while ubiquinol is the active, reduced antioxidant form. Ubiquinol is generally considered more bioavailable, especially for older adults, but it is also more expensive.

Because CoQ10 can cause insomnia in some people, it is often recommended to take it in the morning or early afternoon. However, it is a fat-soluble supplement, so it is best absorbed when taken with a meal that contains fat, regardless of the time of day.