Coenzyme Q10 is present in every cell of the body where it helps the mitochondria make energy.
Dietary Sources of CQ10
Foods should always be considered the first source of vitamins, minerals, and other nutritional factors. However, with CQ10, dietary sources contain very minor amounts compared to those found to be effective in clinical studies. According to an article in Critical Reviews of Food Science and Nutrition , “The average dietary intake of CoQ 10 is only 3–6 mg” per day. Meat, fish, nuts, and some oils are the best sources of CoQ 10.
Compare this to the typical 100-300 mg dosage range found to be effective in clinical studies. CQ10 supplements dosages generally range between 50 and 300 mg/day and are safe in people taking them for up to 5 years. 
Who Should Consider CQ10
Congestive Heart Failure
Population research shows that low CQ10 level seems to be associated with congestive heart failure. In fact, they may even be a predictor of mortality. Most studies use between 30 and 300 mg of CQ 10 daily. A 2017 review of the research concluded that patients with heart failure who used CQ10 had lower mortality and higher exercise capacity improvement than placebo treated patients. 
Diabetic Nerve Pain
A randomized trial, the most reliable type of research, showed that 400 mg of CQ10 for 12 weeks improved neuropathic pain in people who had diabetic polyneuropathy. 
Natural Medicines, TM reports that fibromyalgia research showed that 400 mg per day of CQ10 for three months reduced pain and sleep disturbances by about a third and fatigue by 20%. Another study showed that 300 mg per day for 40 days reduced pain, fatigue, tiredness, and tender points by around half. And the patients also had reduced depression. 
Before Cardiac Surgery or After a Heart Attack
Cardiac bypass surgery is associated with damage due to low oxygen during the surgical procedure. Natural Medicines, TM states that one study of people taking 300 mg per day for two weeks before bypass surgery subjective quality-of-life after three years. Other studies on the lower dose of 100 mg per day showed no effect on cardiac function after bypass surgery. 
When heart attack patients were started on CQ10 within 3 days of myocardial infarction, one study found that it reduced cardiac events by about half. .
CQ10 has been studied at a dose of 100 mg/day and is effective. American Academy of Neurology Guidelines considers coenzyme Q10 supplementation to be possibly effective for migraine prevention. 
Other Health Conditions
Some studies have also found CQ10 to have benefits in multiple sclerosis, certain types of muscular dystrophy, HIV/AIDS, and Peyronie disease.
CQ10 has generally not been found effective in helping fatigue related to chemotherapy, post-polio syndrome, or Huntington’s disease. It is also unlikely to benefit athletic performance.
Although statins are known to reduce CQ10 blood levels, and some studies have found that supplementation of CQ10 improves muscle pain , larger studies of the overall literature have not concluded that CQ10 should be routinely recommended .