Can CoQ10 cause anxiety? This question concerns many people considering coenzyme Q10 supplementation. CoQ10 is a naturally occurring compound vital for cellular energy production and antioxidant protection. Whilst generally well-tolerated, understanding potential side effects is essential for safe use. Current medical evidence does not establish a causal link between CoQ10 and anxiety, though individual responses to supplements vary. This article examines the evidence surrounding CoQ10 and anxiety, explores its safety profile, identifies who should exercise caution, and provides guidance on appropriate use. If you experience anxiety symptoms after starting any supplement, consult your GP to rule out other causes and discuss whether supplementation is suitable for your circumstances.

What Is CoQ10 and How Does It Work in the Body?

Coenzyme Q10 (CoQ10), also known as ubiquinone, is a naturally occurring compound found in virtually every cell of the human body. It plays a crucial role in cellular energy production within the mitochondria—the powerhouses of cells—where it participates in the electron transport chain to generate adenosine triphosphate (ATP), the primary energy currency of cells.

Beyond its role in energy metabolism, CoQ10 functions as a potent antioxidant, protecting cell membranes and lipoproteins from oxidative damage caused by free radicals. The body produces CoQ10 endogenously, with highest concentrations found in organs with high metabolic demands, including:

• The heart

• Liver

• Kidneys

• Pancreas

However, endogenous CoQ10 production naturally declines with age, typically beginning after the age of 30. Certain medications, particularly statins (HMG-CoA reductase inhibitors), can lower plasma CoQ10 levels by inhibiting the same biochemical pathway responsible for both cholesterol and CoQ10 synthesis, though the clinical significance of this for symptoms remains unclear.

CoQ10 supplements are available in two forms: ubiquinone (the oxidised form) and ubiquinol (the reduced, active form). The body can interconvert between these forms, and absorption may vary between different formulations. Dietary sources of CoQ10 include oily fish (such as mackerel and sardines), organ meats, whole grains, and certain vegetables, though supplementation provides significantly higher doses than can be obtained through diet alone.

In the UK, CoQ10 is generally sold as a food supplement and is not a licensed medicine. While research has explored CoQ10's potential role in various conditions, including heart failure, migraine prevention, and neurodegenerative diseases, it's important to note that UK clinical guidelines do not currently recommend CoQ10 as a treatment for these conditions.

Potential Side Effects of CoQ10 Supplements

CoQ10 is generally well-tolerated by most individuals, with a favourable safety profile established through numerous clinical trials. In the UK, CoQ10 is typically marketed as a food supplement (regulated under food law) rather than as a licensed medicine, reflecting its relatively benign nature. However, as with any supplement, some individuals may experience adverse effects.

The most commonly reported side effects are gastrointestinal in nature and typically mild, including:

• Nausea

• Diarrhoea

• Abdominal discomfort

• Loss of appetite

• Heartburn

Other occasionally reported effects include headache, dizziness, fatigue, insomnia, and skin rashes. These effects are generally dose-dependent and often resolve with dose reduction or when taking the supplement with food.

Regarding anxiety specifically, there is no established causal link between CoQ10 supplementation and anxiety in the medical literature. Some preliminary research has explored whether CoQ10 might have anxiolytic (anxiety-reducing) properties due to its role in mitochondrial function and oxidative stress reduction, but this research remains in very early stages and is inconclusive. No UK clinical guidelines recommend CoQ10 for anxiety management.

That said, individual responses to supplements can vary considerably. Some people may experience subjective feelings of restlessness or nervousness when starting CoQ10, though it is unclear whether this represents a direct pharmacological effect or relates to other factors such as:

• Coincidental timing with life stressors

• Heightened awareness of bodily sensations when starting a new supplement

• Interactions with other medications or supplements

• Underlying anxiety conditions

If you experience new or worsening anxiety symptoms after starting CoQ10, it is advisable to discontinue the supplement and consult your GP to rule out other causes and discuss whether CoQ10 is appropriate for your individual circumstances. For severe anxiety, panic attacks, or thoughts of self-harm, seek urgent help via NHS 111 or call 999 in an emergency.

Any suspected adverse reactions to supplements can be reported through the MHRA Yellow Card scheme (www.mhra.gov.uk/yellowcard).

Who Should Avoid or Use Caution With CoQ10?

While CoQ10 is safe for most adults, certain groups should exercise caution or avoid supplementation without medical supervision. Understanding these contraindications and precautions is essential for safe use.

Individuals taking anticoagulant medications, particularly warfarin, should use CoQ10 with caution. There have been reports suggesting CoQ10 may reduce warfarin's anticoagulant effect, potentially affecting INR (International Normalised Ratio) values. If you take warfarin and wish to use CoQ10, your GP or anticoagulation clinic should monitor your INR more frequently and may need to adjust your warfarin dose accordingly. Always inform your anticoagulation service if you start or stop taking CoQ10.

Pregnant and breastfeeding women should avoid CoQ10 supplements due to insufficient safety data in these populations. Whilst there is no evidence of harm, the precautionary principle applies when evidence is limited.

People with diabetes should monitor blood glucose levels carefully when starting CoQ10, as some evidence suggests it may affect glycaemic control, though findings are inconsistent. Discuss supplementation with your diabetes care team, particularly if you take glucose-lowering medications.

Other groups requiring caution include:

• Individuals undergoing cancer treatment: Discuss with your oncology team before using CoQ10, as evidence is limited and there are theoretical concerns it might interact with some treatment regimens

• Those with low blood pressure: CoQ10 may have mild hypotensive effects

• People scheduled for surgery: Follow your pre-assessment team's advice regarding supplements; generally, it's advisable to inform your surgical team about all supplements you're taking

Children should not take CoQ10 supplements without paediatric specialist advice, as safety and appropriate dosing in this age group have not been well established. If you have any chronic health conditions or take regular medications, always consult your GP or pharmacist before starting CoQ10 supplementation to ensure it is safe and appropriate for your individual circumstances.

Safe Use of CoQ10: Dosage and Monitoring Guidance

For those considering CoQ10 supplementation, understanding appropriate dosing and monitoring is essential for both safety and potential benefit. As CoQ10 is classified as a food supplement in the UK, it is not subject to the same regulatory oversight as licensed medicines, making informed consumer choices particularly important.

Typical dosage ranges used in clinical studies vary from 90 mg to 200 mg daily for general supplementation. Higher doses (up to 300–600 mg daily in divided doses) have been studied in research settings for specific conditions, but such high-dose supplementation should only be considered under healthcare professional supervision.

It's important to note that despite common claims, the National Institute for Health and Care Excellence (NICE) does not recommend CoQ10 for statin-associated muscle symptoms, as evidence for its efficacy is insufficient.

To optimise absorption, take CoQ10 with a meal containing fat, as it is a fat-soluble compound. Dividing the daily dose (e.g., taking it twice daily rather than once) may improve tolerability and absorption. Different formulations may have varying bioavailability, though the body can convert between the ubiquinone and ubiquinol forms.

Quality considerations are paramount when selecting supplements. Look for products that:

• Come from reputable UK manufacturers with good manufacturing practice (GMP) certification

• Have clear labelling of CoQ10 content and form

• Include batch or lot numbers

• Provide clear ingredient information

• Athletes should consider products with Informed-Sport certification to reduce contamination risk

Monitoring and safety checks should include keeping a symptom diary when starting supplementation to identify any adverse effects. If you experience persistent gastrointestinal symptoms, headaches, or any concerning symptoms including anxiety, discontinue use and consult your GP.

For individuals with pre-existing conditions or taking medications, regular review with your healthcare provider is advisable. This is particularly important for those on anticoagulants, antihypertensive medications, or diabetes treatments. Remember that CoQ10 should complement, not replace, evidence-based medical treatments, and any decision to supplement should be made in consultation with a healthcare professional who understands your complete medical history.

If you experience any suspected adverse reactions, report them through the MHRA Yellow Card scheme (www.mhra.gov.uk/yellowcard).

Frequently Asked Questions