Short answer: Ubiquinone is the standard form of CoQ10; ubiquinol is the reduced form. In a head-to-head study in 21 older adults, ubiquinol was not significantly better absorbed than ubiquinone, and either way CoQ10 showed up in the blood mostly as ubiquinol.1 Most trials used standard CoQ10. NIH says the evidence for heart and statin-pain uses is inconclusive or negative.2
| Ubiquinone (standard CoQ10) | Ubiquinol | |
|---|---|---|
| What it is | The oxidised form; used in most CoQ10 studies3 | The reduced form3 |
| Absorption, head to head | Reference product in a 3-way crossover of 100 mg single doses1 | 1.7 times the reference, not statistically significant1 |
| Form found in the blood | Mostly ubiquinol, even when taken as ubiquinone1 | Mostly ubiquinol1 |
| Larger trials | Heart failure: 420 people, 100 mg 3 times a day for 2 years; fewer major heart events4 | 54 active men, 300 mg a day for 6 weeks; no change in exercise capacity3 |
| Safety | No serious side effects reported; may interact with warfarin and insulin2 | No safety concerns up to 300 mg a day for 4 weeks in the maker's study5 |
In a randomized crossover study, 21 healthy adults aged 65 to 74 took single 100 mg doses of a water-soluble CoQ10, ubiquinol capsules, and standard ubiquinone capsules a week apart. Ubiquinol was 1.7 times the ubiquinone level over 48 hours, but this was not statistically significant; the water-soluble product was 2.4 times. All three showed up in the blood mostly as ubiquinol.1
The first human study of ubiquinol, by Kaneka (the maker), found it was absorbed and caused no safety concerns at up to 300 mg a day for 4 weeks.5
The Q-SYMBIO trial gave 420 people with moderate to severe heart failure 100 mg of CoQ10 3 times a day or placebo for 2 years. Short-term measures did not change, but major heart events were lower (15% vs 26%). The abstract does not name the form.4 NCCIH calls the heart failure evidence inconclusive overall and says the evidence does not support CoQ10 for statin muscle pain.2
In 54 healthy, active men, 300 mg a day of ubiquinol for 6 weeks raised blood CoQ10 and one measure of mitochondrial efficiency, but did not change time to exhaustion. Kaneka co-funded the work.3
The one head-to-head absorption study found no significant edge for ubiquinol, and the body converts most of either form to ubiquinol. No trial has compared the two on a health outcome. This is general information, not personal advice. More detail: the Coenzyme Q10 (CoQ10) guide.