Ubiquinol is well tolerated by most adults, but some people should not start it without medical advice. Check with your doctor first if you take the blood thinner warfarin, are having chemotherapy or radiation therapy, are pregnant or breastfeeding, have blood pressure that runs low or take medicines that lower blood pressure or blood sugar, or have surgery coming up. These cautions come from the National Center for Complementary and Integrative Health (NCCIH) and the National Cancer Institute's PDQ summary on coenzyme Q10 (CoQ10).
Key Takeaways
- Ubiquinol is the reduced form of CoQ10. The body converts ubiquinol and ubiquinone back and forth, so the same safety cautions apply to both.
- Talk to your prescriber before taking it if you use warfarin, insulin or other blood-sugar-lowering medicines, or blood pressure medicines.
- If you are having chemotherapy or radiation therapy, ask your oncology team first; long-term effects alongside these therapies have not been studied.
- There are no safety data for CoQ10 supplements in pregnancy or breastfeeding, so ask your healthcare provider before using it.
- Tell your surgical team about every supplement you take, ideally weeks before an operation.
- For most other adults, no serious side effects have been reported; mild sleep trouble and stomach upset are the most common complaints.
Evidence grade: Moderate. The cautions below come from NIH summaries that agree with each other, but many are based on small trials, case reports or known chemistry rather than large studies of ubiquinol itself.
What Ubiquinol Is
CoQ10 is a compound your body makes and uses to produce energy in cells and to protect cells as an antioxidant. The highest levels are in the heart, liver, kidneys and pancreas, and levels fall as people get older.
CoQ10 exists in two forms. Ubiquinone is the oxidized form and ubiquinol is the reduced form. Inside cells the two are converted back and forth all the time, and CoQ10 travels in the blood mostly as ubiquinol, whichever form you swallow. A 2020 review notes that ubiquinol is not "the active form" in any special sense. That matters for safety: research on CoQ10 in general applies to ubiquinol too. For a full comparison of the two forms, see our ubiquinone vs ubiquinol guide.
Who Should Not Take Ubiquinol Without Medical Advice
The groups below are not told "never take it." They are the people for whom a doctor, pharmacist or other clinician should weigh in first.
People taking warfarin
The National Cancer Institute (NCI) states that CoQ10 can reduce the body's response to warfarin, and NCCIH lists warfarin as a possible interaction. Human data are mixed: a 2015 review of supplements and surgery notes that one controlled trial did not show a consistent effect, while a report of 171 patients linked CoQ10 with warfarin to a higher bleeding risk. Because a change in warfarin response can matter, do not start or stop ubiquinol on your own. Talk to your prescriber, who may want to check your blood tests more often.
People having chemotherapy or radiation therapy
NCCIH says CoQ10 may not be compatible with some types of cancer treatment. The NCI patient summary adds that trials using CoQ10 during chemotherapy and radiation therapy have not followed people long enough to know whether it made treatment less effective. An observational study of people treated for breast cancer linked antioxidant supplements, including CoQ10, taken before and during treatment with a trend toward more recurrence. That finding is not proof of harm, but it is why oncology teams usually want to approve any supplement first.
Pregnant or breastfeeding women
There is not enough research to say CoQ10 supplements are safe during pregnancy or breastfeeding. The NIH's LactMed database notes that CoQ10 is a normal part of breast milk, but no data exist on the safety of supplementation in nursing mothers or infants. NCCIH points out that many supplements have never been tested in pregnant or nursing women. If you are pregnant, trying to conceive or breastfeeding, ask your healthcare provider before taking ubiquinol.
People with low blood pressure, or taking blood pressure or blood-sugar medicines
Research on CoQ10 and blood pressure is inconsistent. A 2007 analysis of older, mostly small studies reported drops of up to 17 mm Hg systolic. A 2016 Cochrane review of the better-designed trials found no clinically significant change, and NCCIH says CoQ10 probably does not have a meaningful effect on blood pressure. Dizziness is one of the side effects NCI lists.
The medicine side is clearer. NCI notes that drugs used to lower blood pressure or blood sugar may lower CoQ10 levels or its effects, that beta-blockers can inhibit CoQ10-dependent enzyme reactions, and that CoQ10 may reduce insulin requirements. If your blood pressure tends to run low, or you take medicines for blood pressure or blood sugar, talk to your prescriber before starting ubiquinol so your readings can be watched.
People preparing for surgery
NCCIH advises telling your health care providers about every supplement as far in advance of an operation as possible, because some supplements may increase bleeding risk or affect the response to anesthesia. A 2015 review of supplements and blood clotting during surgery included CoQ10 and concluded that, because these effects are hard to predict, it is prudent to stop supplements before surgery. Your surgeon or anesthesiologist will tell you when to stop and when to restart.
People with a known sensitivity to the product
Anyone who has had a reaction such as a rash after taking CoQ10, or who is sensitive to an ingredient in a particular product, should avoid that product and read the full ingredient list before trying another.
| Situation | Why caution is advised | What to do |
|---|---|---|
| Taking warfarin | CoQ10 may reduce the response to warfarin (NCI, NCCIH) | Talk to your prescriber before starting or stopping |
| Chemotherapy or radiation therapy | May not be compatible with some treatments; long-term effects unstudied | Ask your oncology team first |
| Pregnancy or breastfeeding | No safety data for supplementation | Ask your healthcare provider |
| Low blood pressure, or blood pressure medicines | Mixed research on blood pressure; possible interaction with these medicines | Talk to your prescriber and monitor readings |
| Insulin or other blood-sugar-lowering medicines | CoQ10 may lower insulin needs | Talk to your prescriber before starting |
| Upcoming surgery | Supplements can affect bleeding or anesthesia in ways that are hard to predict | Tell your surgical team weeks ahead |
Is Ubiquinol Safe for Everyone Else?
For healthy adults who are not in any of the groups above, the safety record is good. NCCIH reports no serious side effects. In a placebo-controlled study, healthy volunteers took 90, 150 or 300 mg of ubiquinol a day for four weeks with no clinically relevant changes in lab tests, vital signs or heart tracings. A safety review of CoQ10 trials found that stomach complaints were no more common at 1,200 mg a day than at 60 mg, and identified 1,200 mg a day as an observed safe level.
Taking CoQ10 with a meal that contains some fat helps absorption, and if it affects your sleep you can take it earlier in the day. See the best time to take CoQ10 for more on timing.
If Ubiquinol Is Right for You
Check with your doctor first if any of the situations above apply to you. If none do and your clinician agrees, a standard supplement is a reasonable option. OPA CoQ10 Ubiquinone provides 200 mg of CoQ10 as ubiquinone in one capsule, with a cellulose vegetable capsule and rice flour as the other ingredients; a bottle holds 30 capsules, a 30-day supply. It contains ubiquinone rather than ubiquinol, and as explained above the body converts between the two forms. Its 200 mg amount sits within the 90 to 390 mg a day range NCI reports for human studies, so the same cautions in this article apply to it.
Safety and Interactions
Reported side effects of CoQ10 are usually mild. They include trouble sleeping (noted in some people at 100 mg a day or more), stomach upset, nausea, heartburn, upper abdominal pain, headache, dizziness, rash, tiredness, irritability and sensitivity to light. Long-term use of 300 mg a day has been linked to raised liver enzymes, without reported liver damage.
- Warfarin: talk to your prescriber before taking CoQ10 or ubiquinol.
- Insulin and oral blood-sugar-lowering medicines: talk to your prescriber; CoQ10 may lower insulin needs.
- Blood pressure medicines, including beta-blockers: talk to your prescriber or pharmacist.
- Cholesterol-lowering medicines: NCI notes that statins and gemfibrozil lower blood CoQ10 levels. Keep taking your medicine as prescribed and ask your pharmacist before adding CoQ10.
- Chemotherapy or radiation therapy: ask your oncology team first.
Supplements are not reviewed by the FDA for safety and effectiveness before sale, so quality can differ between brands. Stop taking ubiquinol and contact your healthcare provider if you notice unusual bleeding or bruising, dizziness or fainting.
Frequently Asked Questions
Who should avoid ubiquinol?
People taking warfarin, people having chemotherapy or radiation therapy, pregnant or breastfeeding women, people with low blood pressure or taking blood pressure or blood-sugar medicines, and people with surgery coming up should not start ubiquinol without medical advice.
What are the side effects of ubiquinol?
Most people have none. When side effects occur they are usually mild: trouble sleeping, stomach upset, nausea, heartburn, headache, dizziness or rash.
Can I take ubiquinol every day?
Daily use is how it was taken in studies. Healthy volunteers took up to 300 mg of ubiquinol a day for four weeks without safety concerns, and CoQ10 trials have lasted much longer. Check with your doctor first if any of the cautions in this article apply to you.
Is ubiquinol safer than ubiquinone?
No difference in safety has been shown. The body converts the two forms into each other, so the same cautions and interactions apply to both.
Should I stop ubiquinol before surgery?
Tell your surgical team you take it as early as possible. A review of supplements and surgery advises stopping supplements beforehand; your surgeon or anesthesiologist will tell you when.
Can I take ubiquinol while pregnant or breastfeeding?
There are no safety data for CoQ10 supplements in pregnancy or breastfeeding. Talk to your healthcare provider before taking it.
Sources
- National Center for Complementary and Integrative Health (NIH). Coenzyme Q10. Last updated 2019.
- National Cancer Institute (NIH). Coenzyme Q10 (PDQ)–Health Professional Version. Updated 2024.
- National Cancer Institute (NIH). Coenzyme Q10 (PDQ)–Patient Version.
- National Center for Complementary and Integrative Health (NIH). Using Dietary Supplements Wisely. Last updated 2019.
- Drugs and Lactation Database (LactMed). Coenzyme Q10. National Institute of Child Health and Human Development. 2021.
- Wang CZ, Moss J, Yuan CS. Commonly used dietary supplements on coagulation function during surgery. Medicines (Basel). 2015.
- Ho MJ, Li EC, Wright JM. Blood pressure lowering efficacy of coenzyme Q10 for primary hypertension. Cochrane Database Syst Rev. 2016.
- Rosenfeldt FL, Haas SJ, Krum H, et al. Coenzyme Q10 in the treatment of hypertension: a meta-analysis of the clinical trials. J Hum Hypertens. 2007.
- Mantle D, Dybring A. Bioavailability of coenzyme Q10: an overview of the absorption process and subsequent metabolism. Antioxidants (Basel). 2020.
- Hosoe K, Kitano M, Kishida H, et al. Study on safety and bioavailability of ubiquinol (Kaneka QH) after single and 4-week multiple oral administration to healthy volunteers. Regul Toxicol Pharmacol. 2007.
- Hathcock JN, Shao A. Risk assessment for coenzyme Q10 (ubiquinone). Regul Toxicol Pharmacol. 2006.
Disclosure: OPA Nutrition sells supplements, including products mentioned in this article. This content is for education only and is not medical advice. Statements about dietary supplements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease. Talk to your healthcare provider before using any supplement, especially if you take medication or have a medical condition.
Written and reviewed by Michael Gonzales, Founder, OPA Nutrition · Last reviewed: · How OPA researches and writes
