Fish oil with CoQ10 is a popular supplement combination in the UK, with many individuals taking both to support cardiovascular health and overall wellbeing. Fish oil provides omega-3 fatty acids (EPA and DHA), whilst coenzyme Q10 (CoQ10) plays a vital role in cellular energy production and acts as an antioxidant. Although each supplement has been studied individually, high-quality evidence specifically examining their combined use remains limited. Both are classified as food supplements rather than licensed medicines, meaning they have not undergone the rigorous clinical trials required for pharmaceutical products. This article explores the science behind fish oil with CoQ10, safe usage, potential benefits, side effects, and how to choose quality products in the UK.

What Are Fish Oil and CoQ10 Supplements?

Fish oil and coenzyme Q10 (CoQ10) are two of the most widely used dietary supplements in the UK, each with distinct biochemical properties and proposed health benefits.

Fish oil is derived from the tissues of oily fish such as mackerel, salmon, sardines, and anchovies. It is rich in omega-3 polyunsaturated fatty acids, particularly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These long-chain omega-3 fatty acids play crucial roles in cellular membrane structure, inflammatory pathways, and cardiovascular function. The body converts only small amounts from alpha-linolenic acid (ALA), so dietary intake is recommended. Fish oil supplements are available in various forms including soft gel capsules, liquids, and emulsions, with concentrations of EPA and DHA varying between products.

Coenzyme Q10, also known as ubiquinone, is a naturally occurring compound found in virtually every cell of the human body. It functions primarily within the mitochondria—the cellular powerhouses—where it plays an essential role in the electron transport chain and adenosine triphosphate (ATP) production. CoQ10 also acts as a lipid-soluble antioxidant, protecting cell membranes from oxidative damage. The body produces CoQ10 endogenously, but levels decline with age and may be reduced by certain medications, particularly statins. CoQ10 supplements are available in two forms: ubiquinone (the oxidised form) and ubiquinol (the reduced, active form), with some studies suggesting ubiquinol may have higher bioavailability, though the clinical significance remains uncertain.

Both supplements are classified as food supplements in the UK and are primarily regulated by the Food Standards Agency (FSA) and Office for Product Safety and Standards (OPSS). They are not licensed medicines and therefore do not require a prescription, though this also means they have not undergone the rigorous clinical trials required for pharmaceutical products.

Benefits of Taking Fish Oil with CoQ10 Together

Many individuals choose to take fish oil and CoQ10 together, based on the premise that their complementary mechanisms may support cardiovascular health, though it is important to note that there is no official link established by regulatory bodies such as NICE or the MHRA confirming synergistic benefits of this specific combination.

Cardiovascular considerations form the primary rationale for combining these supplements. Omega-3 fatty acids from fish oil have been studied extensively for their effects on triglyceride levels, blood pressure, and inflammatory markers. It's important to distinguish between prescription omega-3 medicines and over-the-counter fish oil supplements. NICE (TA805) recommends icosapent ethyl (a prescription-only, highly purified EPA) for specific high-risk patients, while over-the-counter fish oil supplements are not recommended for cardiovascular disease prevention. CoQ10, meanwhile, has been investigated for its potential role in heart failure and in mitigating statin-related muscle symptoms, though evidence remains mixed. Some practitioners suggest that because statins reduce both cholesterol and CoQ10 synthesis, supplementation may be beneficial for patients experiencing myalgia, although NICE guidance (NG238) does not routinely recommend this approach.

Antioxidant and anti-inflammatory properties represent another theoretical benefit. Both fish oil and CoQ10 possess antioxidant characteristics that may help reduce oxidative stress—a process implicated in numerous chronic conditions including atherosclerosis and neurodegenerative diseases. EPA and DHA are precursors to specialised pro-resolving mediators (SPMs) that help resolve inflammation, whilst CoQ10 protects lipids from peroxidation.

Energy metabolism support is sometimes cited, particularly for individuals experiencing fatigue. CoQ10's role in mitochondrial ATP production, combined with omega-3s' effects on membrane fluidity and cellular signalling, may theoretically support cellular energy processes, though robust clinical evidence for subjective energy improvements remains limited.

It is crucial to emphasise that whilst both supplements have been studied individually, high-quality clinical trials specifically examining the combined use of fish oil and CoQ10 are scarce. This combination should not replace guideline-directed therapy. Patients should maintain realistic expectations and understand that supplements cannot replace evidence-based medical treatments or a balanced diet rich in oily fish, fruits, and vegetables.

How to Take Fish Oil and CoQ10 Safely

When considering fish oil and CoQ10 supplementation, appropriate dosing, timing, and awareness of individual health circumstances are essential for safe use.

Typical dosing recommendations vary depending on the specific health concern. For general cardiovascular support, fish oil supplements providing 250–500 mg combined EPA and DHA daily are commonly suggested. Higher doses (2–4 grams daily) are used for elevated triglycerides but should only be taken under medical supervision and may require prescription-only omega-3 medicines. CoQ10 is typically taken in doses ranging from 100–200 mg daily. Some individuals, particularly those on statins or with heart failure, may use higher amounts (200–300 mg daily), though evidence for clinical benefit remains mixed and is not routinely recommended in NICE guidance. Always check the product label for the actual content of active ingredients, as formulations vary considerably.

Timing and absorption considerations can influence efficacy. Both fish oil and CoQ10 are fat-soluble, meaning they are best absorbed when taken with meals containing dietary fat. Splitting doses throughout the day (e.g., taking half in the morning and half in the evening with food) may improve tolerability and absorption. Some individuals prefer taking fish oil with the largest meal of the day to minimise gastrointestinal side effects.

Special populations require particular caution. Individuals taking anticoagulant or antiplatelet medications (such as warfarin, apixaban, or clopidogrel) should consult their GP or anticoagulation clinic before starting fish oil, as high doses may theoretically increase bleeding risk, though clinically significant interactions are uncommon at standard supplemental doses. Those with fish or shellfish allergies should avoid fish-derived oils and may consider algae-based omega-3 supplements as an alternative. Pregnant or breastfeeding women should seek medical advice before supplementation. They should avoid cod liver oil (due to vitamin A content), follow NHS guidance on oily fish consumption limits, and may consider algae-derived DHA as an alternative.

Patients should contact their GP if they are considering supplements alongside prescribed medications, have existing medical conditions (particularly bleeding disorders, diabetes, or cardiovascular disease), or are planning surgery. For surgery, do not stop supplements without consulting your surgical or anaesthetic team. Never use supplements as a substitute for prescribed medications without medical consultation.

Possible Side Effects and Interactions

Whilst fish oil and CoQ10 are generally well tolerated, users should be aware of potential adverse effects and drug interactions to ensure safe supplementation.

Common side effects of fish oil include:

• Gastrointestinal disturbances: fishy aftertaste, belching, nausea, loose stools, or indigestion are the most frequently reported issues. These can often be minimised by taking supplements with meals, choosing enteric-coated formulations, or refrigerating capsules.

• Fishy body odour or breath: occasionally reported with higher doses.

• Mild increases in bleeding tendency: whilst clinically significant bleeding is rare at standard doses, individuals should be vigilant for unusual bruising or prolonged bleeding from minor cuts.

CoQ10 side effects are generally mild and infrequent but may include:

• Gastrointestinal symptoms: nausea, diarrhoea, or stomach upset, typically dose-related.

• Insomnia or restlessness: some individuals report sleep disturbances, particularly when taking CoQ10 late in the day.

• Skin rashes: rarely reported.

Drug interactions warrant careful consideration. Fish oil may potentiate the effects of anticoagulants and antiplatelet agents, though evidence for clinically significant interactions at supplemental doses is limited. CoQ10 may reduce the effectiveness of warfarin, necessitating more frequent INR monitoring if used concurrently. CoQ10 may also modestly lower blood pressure, so monitor if you're taking antihypertensive medications.

When to seek medical attention: Call 999 immediately for severe allergic reactions (difficulty breathing, facial swelling) or uncontrolled bleeding. Contact your GP promptly if you experience unusual bleeding or bruising, severe abdominal pain, or any concerning symptoms after starting supplementation. If you are taking multiple medications or have complex health conditions, a medication review with your GP or pharmacist is advisable before adding supplements to your regimen. Remember that supplements can interact with herbal remedies and over-the-counter medications as well as prescription drugs.

If you experience any suspected side effects, report them through the MHRA Yellow Card scheme (yellowcard.mhra.gov.uk).

Choosing Quality Fish Oil and CoQ10 Supplements in the UK

The UK supplement market is vast and variable in quality, making informed product selection essential for safety and efficacy.

Regulatory standards and certifications provide important quality indicators. Look for products that comply with food safety standards such as ISO 22000/HACCP or BRCGS (British Retail Consortium Global Standard). Whilst food supplements are not licensed medicines in the UK, reputable manufacturers voluntarily adhere to quality standards. Third-party testing certifications such as IFOS (International Fish Oil Standards) for omega-3 products or Informed Sport for sports supplements indicate that products have been tested for purity, potency, and contaminants.

For fish oil supplements, key quality markers include:

• Purity and contaminant testing: high-quality fish oils should be tested for heavy metals (mercury, lead), polychlorinated biphenyls (PCBs), and dioxins. Look for products that provide certificates of analysis or transparency about testing.

• Omega-3 concentration: check the actual EPA and DHA content per serving, not just the total fish oil amount. A 1000 mg fish oil capsule may contain only 300 mg of combined EPA/DHA.

• Form and bioavailability: fish oil is available as natural triglycerides, ethyl esters, or re-esterified triglycerides. While some studies suggest triglyceride forms may be better absorbed, the clinical significance is uncertain; focus on verified EPA/DHA content and freshness.

• Freshness: omega-3 fatty acids are susceptible to oxidation. Check expiry dates and consider products with added antioxidants like vitamin E.

For CoQ10 supplements, consider:

• Form: ubiquinol (reduced form) versus ubiquinone (oxidised form). Ubiquinol may offer better bioavailability in some studies, particularly for older adults, though formulation also affects absorption.

• Dosage and formulation: CoQ10 absorption is enhanced by lipid-based delivery systems or when combined with oils.

Practical purchasing advice: Purchase from reputable pharmacies, health food shops, or established online retailers. Be cautious of products making exaggerated health claims, as these violate UK advertising standards. Price is not always indicative of quality, but extremely cheap products may cut corners on purity testing. Check for clear allergen declarations, particularly for fish or gelatin. Pregnant women should avoid cod liver oil supplements due to vitamin A content. Consider consulting a registered dietitian or pharmacist for personalised recommendations, particularly if you have specific health conditions or are taking multiple medications. Remember that supplements should complement, not replace, a balanced diet rich in oily fish, wholegrains, fruits, and vegetables.

Frequently Asked Questions