Which Form of CoQ10 is Better Absorbed?
Ubiquinol (the reduced form) demonstrates superior bioavailability compared to ubiquinone (the oxidized form), achieving significantly higher plasma CoQ10 levels at equivalent doses. 1
Evidence for Superior Ubiquinol Absorption
The most definitive evidence comes from a controlled crossover trial in healthy volunteers comparing 200 mg/day of each form:
Ubiquinol supplementation increased plasma total CoQ10 from 0.9 to 4.3 µg/mL, while ubiquinone only increased levels from 0.9 to 2.5 µg/mL—representing a 1.7-fold advantage for ubiquinol 1
The CoQ10/cholesterol ratio increased to 1.2 µmol/mmol with ubiquinol versus only 0.7 µmol/mmol with ubiquinone, demonstrating statistically superior bioavailability (P < 0.001) 1
In older men specifically, ubiquinol increased plasma total CoQ10 1.5-fold after just 2 weeks, while ubiquinone produced no significant increase—suggesting ubiquinol may be particularly advantageous in aging populations 2
The Stability Controversy
There is conflicting evidence regarding whether ubiquinol remains stable during digestion:
Dog studies suggest ubiquinol oxidizes to ubiquinone in the acidic gastrointestinal environment, with increasing conversion as it passes through the stomach and small intestine 3
However, mouse studies directly contradict this, showing that orally administered ubiquinol reaches the small intestine and is absorbed "mostly in its original form" without significant oxidation 4
Despite this mechanistic debate, the clinical outcome data consistently shows ubiquinol achieves higher plasma levels regardless of the absorption mechanism 1, 2
Practical Formulation Considerations
Both forms have inherently poor intestinal absorption due to high lipophilicity and large molecular weight, with peak plasma levels occurring 5-10 hours post-ingestion 5, 6
Taking CoQ10 with fat-containing meals significantly enhances absorption for both forms, given the lipid-soluble nature 6
Newer cocrystal formulations of ubiquinol with nicotinamide show 2.2 times higher maximum concentrations and 4.5 times greater AUC compared to standard marketed ubiquinol forms, representing a potential future advancement 7
Clinical Dosing Implications
The 2022 ESPEN guidelines note that CoQ10 is available as either ubiquinol or ubiquinone, but do not specify a preference between forms 5
Therapeutic doses of 100-200 mg/day appear optimal, following a U-shaped dose-response curve where higher doses show diminishing absorption returns 5, 8
Individual response varies: approximately 60% of subjects respond better to ubiquinol, while 20% may respond better to ubiquinone, suggesting some inter-individual variability 2
Common Pitfall to Avoid
Do not assume equivalent dosing between forms—if switching from ubiquinone to ubiquinol, the dose may need adjustment downward given the superior bioavailability, particularly when monitoring plasma levels or clinical endpoints 1