How much NMN must I take to be effective?
The most effective doses to prevent age-related illness in rodents are about 300 mg/kg. This means that a 75 kg (about 165 lbs.) person would require 22,500 mg (22.5 grams). This dose would cost over $100 per dose; if taken daily, it would cost over $35,000 annually.
However, larger organisms like humans do not need large doses of the substance to be effective. According to a scientific theory called "volume distribution," rodents like mice need higher doses of substance than humans. A reasonable quantity of 300 mg/kg in mice would amount to 24.39 mg/kg in humans. For this same effect, a 75 kg person would need approximately 1.829 g. Remember that the 300mg/kg dose of NMN is considered high. Now it's time to ask: "How much NMN do I need to get to have a significant impact?" 
A study in mice showed that 100 mg/kg per day reduced most of the age-related physiological decline. This means that an adult with an average weight of 62 kilograms (or 137 lbs.) should take 500 mg daily. To match the rodent's "distribution volume," the human dose is divided by 12.3. According to this calculation, a 90 kg adult should consume approximately 750 mg daily.
How much is NMN used in human studies?
A Japanese research team has conducted a human clinical trial to test the safety of oral doses of up to 500 mg NMN (nicotinamide mononucleotide). They found no change in physiological measures such as heart rate or blood pressure. The study confirms that a single amount of NMN (nicotinamide mononucleotide) up to 500 mg is safe and well tolerated.
Washington University School of Medicine in St. Louis found that oral doses of 250mg NMN daily for ten weeks improved insulin sensitivity and structure in older women. These results show that NMN (nicotinamide mononucleotide) doses as low as 250 mg daily are safe and effective in increasing muscle insulin sensitivity .
A study by the University of Tokyo also showed that men over 65 could benefit from 250 mg of NMN daily for 12 weeks. Supplementation with NMN (nicotinamide mononucleotide) has improved grip strength, speed, and the ability to get up from a sitting position.
NMN (nicotinamide mononucleotide) safety is subject to clinical trials. Long-term 200 to 300 mg/day administration for 24 weeks may occur. Middle-aged and older people with age-related problems such as diabetes, high blood pressure, obesity, malnutrition, and glucose metabolism are tested for the efficacy of NMN to improve their cardiometabolic function and glucose metabolism .
What is the right amount?
After taking into account the safety and efficacy studies in humans and animals and calculating the optimum dose of NMN (nicotinamide mononucleotide), 500 mg is the recommended daily intake for adults aged 30 to 60 years. People over the age of 65 may consume 750 mg daily safely to maximize the benefits of NMN . However, a recent double-blind placebo-controlled Human study showed that 150 mg of NMN taken for 60 days will increase NAD+.