Does CoQ10 have any negative side effects?


Coenzyme Q10 (CoQ10) is a popular nutritional supplement taken by millions of people worldwide. This antioxidant nutrient plays important roles in energy production and protecting the body from oxidative damage.

While CoQ10 supplements are considered very safe overall, some people wonder if there are any potential negative side effects to be aware of. Let’s closely examine what the research says.

Does CoQ10 have any negative side effects?

What is CoQ10?

Before looking at side effects, it’s helpful to understand what CoQ10 is and why people take it:

  • CoQ10 is a compound made naturally by the body and stored in cell mitochondria.
  • It helps generate adenosine triphosphate (ATP), the main energy molecule.
  • It also functions as a powerful antioxidant.
  • Food sources include meat, fish, nuts, seeds, and oils.
  • Levels start decreasing around age 40.

People take CoQ10 supplements to help:

  • Increase low energy levels
  • Improve heart health
  • Support cognitive function
  • Enhance athletic performance
  • Protect cells from oxidative damage

But are there any potential downsides? Let’s review what studies reveal about safety and side effects.

Common Minor Side Effects

Clinical research shows CoQ10 supplements are generally well tolerated by most people at commonly recommended dosages. However, some minor temporary side effects can occur:

  • Headaches - Tension headaches are occasionally reported with CoQ10 use. These tend to be mild and typically subside within a few days.
  • Upset stomach - Stomach pains, nausea, diarrhea or other gastrointestinal effects may result. Taking CoQ10 with food often minimizes irritation.
  • Insomnia - Some people note slight insomnia or sleep difficulties when taking CoQ10 close to bedtime. Switching to a morning dose usually resolves this.
  • Fatigue - While uncommon, a small percentage of users report increased tiredness or fatigue when starting CoQ10. This is likely temporary adjustment.
  • Dizziness - Occasional dizziness, lightheadedness or vertigo is sometimes reported with CoQ10 supplements. Reducing the dosage may help alleviate it.
  • Skin rashes - Topical and oral CoQ10 preparations rarely cause mild rashes or itching. This typically goes away once use is discontinued.

These types of mild side effects tend to be uncommon and often resolve on their own with continued responsible use. But consult a doctor if any reactions concern you.

Rare Serious Side Effects

Very few serious adverse side effects from CoQ10 supplementation have been reported in studies and literature reviews:

  • Low blood sugar - CoQ10 can slightly lower blood sugar levels. This is usually only a concern for diabetics on medications, requiring monitoring.
  • Lowered blood pressure - In some cases, CoQ10 modestly reduces blood pressure. Adjustments to hypertension medications may be needed.
  • Increased liver enzymes - Liver function tests may reveal elevated enzymes in some individuals, indicating possible toxicity. Discontinuing use typically reverses this.
  • Bleeding risks - Very high doses of CoQ10 could potentially interfere with blood clotting and interact with anticoagulant drugs like warfarin.
  • Allergic reactions - As with any supplement, allergies to CoQ10 or additives are possible but very rare. Discontinue use if signs of allergy develop.

These serious side effects are not common and virtually only occur under certain circumstances in predisposed individuals or with irresponsible use.

Side Effects Risk Factors

A few factors that may increase the risk of side effects from CoQ10 include:

  • High doses - Doses above 200-300 mg per day raise side effect likelihood, especially on an empty stomach.
  • Medication interactions - CoQ10 may interact with blood thinners, chemotherapy drugs, diabetes drugs, thyroid hormones, and certain other medications.
  • Underlying health conditions - Those with diabetes, liver disease, heart problems, or bleeding disorders could be more susceptible to adverse effects.
  • CoQ10 sensitivity - A small percentage of people appear to be more sensitive and prone to side effects from CoQ10 for unknown reasons.
  • Quality issues - Contaminated products or formulations with poor bioavailability may increase side effect incidence. Reputable brands are ideal.

However, the large majority of healthy adults tolerate normal CoQ10 dosages without issues by following recommended usage guidelines.

Long-Term Safety

Numerous studies confirm that CoQ10 has an excellent safety profile with minimal side effects for long-term use:

  • Well tolerated up to 10 years of daily use.
  • No toxic effects identified with continual intake of up to 3000 mg per day.
  • Not shown to be mutagenic or carcinogenic.
  • No known negative impact on organ health or function.
  • No lasting side effects or post-supplementation symptoms.
  • Extremely low reports of withdrawal or dependency.

Evidence does not suggest any specific health risks or safety concerns with prolonged daily CoQ10 supplementation in healthy populations.

But periodic lab testing to monitor liver enzymes, blood cell counts, and electrolyte balance is wise for long-term use under medical supervision.

Side Effects Risk Assessment

When evaluating potential side effects, it’s important to weigh the demonstrated benefits versus potential risks based on current evidence:

  • Benefits are proven for diseases like heart failure, migraines, diabetes, infertility, neurodegenerative disorders, and statin side effects.
  • Hundreds of studies confirm safety and efficacy for supplementation.
  • Potential side effects are typically mild, temporary, and uncommon.
  • Serious adverse effects are very rare when used appropriately.
  • It has low toxicity even at very high doses.

For the large majority of people, research consistently shows the benefits of CoQ10 greatly outweigh the negligible risks. But individual circumstances differ.

Who Should Use Caution With CoQ10?

Despite the overall safety record, certain groups should exercise more caution with CoQ10:

  • Pregnant or breastfeeding women - Lacking data on use for pregnant women, a conservative approach is recommended.
  • Those with bleeding disorders - Potential interference with clotting is theoretically possible. Monitor use with medical providers.
  • Organ transplant recipients - Possible lowering of immunosuppressant effectiveness requires caution.
  • Elective surgery patients - Discontinue CoQ10 at least 2 weeks before any scheduled surgery.
  • Cancer patients - Discuss use of antioxidants with your oncologist before supplementation.

CoQ10 supplements are likely safe for most in these categories under medical guidance. But specialized oversight is advisable.

How to Minimize Side Effects

If you do experience unpleasant side effects from CoQ10, there are some strategies to help minimize them:

  • Take CoQ10 with food to improve tolerance, especially if stomach upset occurs.
  • Reduce your dosage and build up gradually over 2-4 weeks to acclimate.
  • Split dosage into smaller amounts taken twice daily instead of one large dose.
  • Try a different brand or formulation for better bioavailability.
  • Time doses wisely to work around side effects (e.g. morning only dosing if insomnia occurs).
  • Stay hydrated and drink plenty of water daily while supplementing.
  • Notify your doctor about side effects to review your regimen and medical history.

Fortunately, most side effects are manageable by making dosage adjustments, taking with food, or using divided doses.

Does CoQ10 have any negative side effects? Conclusion

In summary, CoQ10 supplements have an impressive safety track record based on extensive research. Serious adverse effects are very rare when taken as recommended under medical guidance.

Mild side effects like headaches, sleep problems, GI discomfort, or dizziness may occur in some users but can often be minimized with sensible precautions and dosing adjustments.

A small percentage of people do appear prone to CoQ10 side effects for unknown reasons. While considered very safe for most, caution is advised for pregnant women, those taking anticoagulants, and people with underlying health conditions.

Overall, studies consistently demonstrate the substantial benefits of CoQ10 supplementation far outweigh the low risk of side effects for most individuals. But work closely with your doctor to determine if CoQ10 is appropriate for your individual health profile and circumstances.


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Resources used to write this article

On CoQ10 overview:

Onminor side effects:

On serious side effects and safety:

On long-term use:

On precautions and risk groups:

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