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We generally advise against purchasing supplements by mail during very hot weather, as high temperatures can damage probiotics, vitamins, and phytochemicals found in herbs.

Ubiquinol is naturally produced in the body, so it can certainly withstand temperatures in the high 90s Fahrenheit. Exposure to higher temperatures will hasten degradation, but the process takes time. For example, an experiment with CoQ10 (a compound similar to ubiquinol) found a loss of only 15% after two months of being exposed to a temperature of 131 Fahrenheit. However, the addition of antioxidants, such as ascorbic acid (vitamin C), could minimize the loss to less than 5% (Kommuru, Chem Pharm Bull, 1999). Ubiquinol and CoQ10 products generally include antioxidant ingredients.

At a temperature of over 140 degrees, the gelatin in softgels can melt and this heat can also damage ubiquinol and CoQ10. If a break occurred in the softgel shell, exposure to air would speed degradation of the ingredient due to oxidation.

Since your softgels didn't melt and it is likely that the product may only have been exposed to high heat for a period of hours or days during transport, there was probably little degradation of the ubiquinol and it should be potent. To extend its shelf-life, store it at room temperature and away from light if it is in a clear bottle. 

For more information, including's tests and comparisons of products, see the CoQ10 and Ubiquinol Supplements Review.

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James 21566
December 12, 2020

I recently purchased two (they were on sale) Qunol Mega CoQ10 100mg , exp year 2024, from Costco. Upon opening one of the bottles I observed that the pills had congealed and clumped together. Is this a quality issue? I've made two calls [left messages for a return call] to Quten Research Institute to report this issue. I've yet to hear from Quten. I am returning both bottles of Qunol to Costco for a refund.

I have no financial interest in Qunol nor a competing CoQ10 producer.

April 6, 2021

I spoke with a representative from Qunol who said the leakage has been traced to their product being stored close to a heat source. Qunol is replacing my 2 bottles of affected CoQ10. I have no financial interest in Qunol nor a competing CoQ10 producer.

August 29, 2021

I've had an experience identical to James 21566. I contacted Qunol and they refused to replace the product and insisted that I take it back to Costco for an exchange.

August 2, 2017

No one knows this better than the big vitamin e-tailers. Ever notice how their best discount offers always arrive during the hot months? There's a reason!
The interior of a UPS/FedEx/USPS truck exposed to a few hours of summer sun can go way over 100 degrees F. Will never forget one clear summer day opening a midday UPS delivery and how HOT the bottles were. "This can't be good," I thought.
Since then we buy a year's worth of everything during the winter months and store it ourselves.

April 25, 2018

Thanks for your post.

August 2, 2017

You mentioned the effect of heat on CoQ10. I'd be interested in a list of other supplements that are vulnerable to heat exposure. Thanks, and keep up the great work, CL.
August 2, 2017

Thank you Alan! Please see this CL Answer about the effects of heat on other types of supplements:

Ken 15344
August 2, 2017

Thank you for this information and, generally, for this sort of information. I've come to lean on you folks for the best available knowledge on matters regarding foods and supplements.
August 2, 2017

Thank you for your kind words, Ken!

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