CoQ10 side effects: what the safety research says

A 2006 safety review of ubiquinone found no dose-related side effects in studies from 60 to 1,200 mg a day: nausea and other stomach complaints were no more common at 1,200 mg than at 60 mg. An industry trade body wrote it, and it can't predict your own reaction. Here is what the sources do and don't say.

What the safety literature found

A 2006 risk assessment of the published ubiquinone trials by the Council for Responsible Nutrition, an industry trade body, concluded that reports of nausea and other gastrointestinal effects could not be causally linked to CoQ10, because there was no dose-response: the effects were no more common at 1,200 mg a day than at 60 mg. It set an observed safe level of 1,200 mg a day, and said data above that were not sufficient for a confident conclusion (Hathcock 2006). Our capsule is 200 mg, one-sixth of that level.

A 2022 meta-analysis of 13 randomised trials in 1,126 people reported a single gastrointestinal adverse event among the 602 participants given CoQ10 (Tsai 2022). A 4-week study of a branded ubiquinol in healthy volunteers at 90 to 300 mg a day found no clinically relevant changes in lab tests, vital signs or ECG; it was run by that product's manufacturer (Hosoe 2007).

What this does not cover: we found no long-term safety study of our specific capsule, and these sources are group results, so they don't rule out an individual reaction.

Our label's cautions

Electric Tiger CoQ10 200 mg carries this warning: do not exceed the recommended dose; ask a physician before use if pregnant or nursing, under 18, taking medication (especially blood thinners) or with a medical condition; keep out of reach of children; do not use if the safety seal is damaged or missing.

Questions people ask

Does CoQ10 have side effects, and what are the side effects of CoQ10 supplements?

The commonly reported ones in the sources above are stomach complaints such as nausea, which the 2006 review found were no more common at higher doses than at low ones. We have no list of rates for our capsule.

Can CoQ10 make you sleepy, or dizzy?

The sources we read did not test sleepiness or dizziness as outcomes, so we can't say how often either happens, or whether CoQ10 causes them. If you feel either after starting, stop and ask a pharmacist or doctor, particularly if you take medication or drive.

Does CoQ10 cause liver or kidney problems? Is it hard on the kidneys?

We found no study in our sources that tested CoQ10's effect on liver or kidney function, so we can't say it is safe or unsafe for either. If you have a liver or kidney condition, ask your doctor before taking it.

Are there side effects for women or men?

None of the safety sources we read reported side effects specific to either sex. Our label advises asking a physician first if you are pregnant or nursing; we give no use guidance for pregnancy.

Does 400 mg of CoQ10 have more side effects?

The 2006 review found no more reports at 1,200 mg than at 60 mg, so 400 mg is inside that range. Our label still says not to exceed the recommended dose, which for our capsule is 200 mg.

What about red yeast rice, or taking it with prescription medicines?

We have not reviewed red yeast rice. For prescription medicines, including statins, see CoQ10 and medications; ask your prescriber before adding a supplement.

Is there a CoQ10 benefit that outweighs the risk?

That is a decision for you and your clinician. We make no benefit claim for our capsule; the trial results at other doses are in the research review. Also see who should not take CoQ10 and how much to take.

When should I stop and see a doctor?

Stop and get medical advice for a rash, swelling of the face or throat, trouble breathing, or any symptom that worries you after starting a supplement.