Here is a list of reported side effects from taking CoQ10:

• nausea
• heartburn
• vomiting
• skin rash
• headache
• fatigue
• flu-like symptoms
• loss of appetite

Notice that most of these side effects are general in nature. Obviously the report of skin rash indicated an allergic reaction to this supplement. (Yes, you can be allergic to even natural supplements.)

Dose as high as 300 mg did not result in significant side effects in most people.

There is not much study done to see if taking Q10 would make existing health conditions worse. We do not believe that most of these interactions are significant.

As a matter of fact, CoQ10 supplements have been shown to make many health problems better!

Nevertheless, here are some theoretical concerns that have been reported in research literatures.

May thin the blood out

There are some reports of people bleeding more when they took coenzyme Q10 supplements. However, this is not confirmed in properly designed studies. Many other factors might have been involved in these cases other than taking Q10 supplements.

But, if you are taking any kind of prescription blood thinners, you should have your INR levels monitored whenever you start or stop any herbs and supplements. This is the common sense approach.

 

May change thyroid levels (hyperthyroidism/hypothyroidism)

For those with a thyroid disorder, there has been a report of changes in the blood levels of thyroid.

 

May lower blood sugar levels

Research studies don't show that Q10 lowers blood sugar level but this effect has been reported. But, hey, isn't this a good thing anyways?

Not much to worry about with regards to side effects. Enjoy all the health benefits of taking CoQ10 supplements!

See the unbiased article Coenzyme Q10 to get a complete list of all the health benefits of taking CoQ10. Suggested dose to use are included.

 See our Unbiased Review on Coenzyme Q10

Selected References for Side Effects of Q10
Revised: August 4, 2011