Niacin is a natural B vitamin found in red wine, grains, and yeast. Its purpose is to scour the blood for toxins that are too gummy or sticky to excrete naturally. Typically the best time to cleanse the blood is when sweating and when the pores are open because of heat. If toxins build up in the blood, you require more niacin to cleanse them, so you may need to increase your dosage if this happens. Your body will tell you how much you need by how strong your flush is. NEVER, I mean NEVER, take the flush-free or time-released forms of niacin. They are not pure nor natural, and are manufactured to NOT flush. The flush can be scary the first time you experience one, and manufacturers want you buying their product again, so they make it in a form to not create a flush. This is VERY toxic to the liver, and will sit in the liver too long. Time-released forms of niacin are made to remain in the liver and assimilate slowly throughout the day - these are highly dangerous to liver health. The body typically ingests all nutrients and processes them within 45 minutes - that's what nature wants.
I take niacin with a light snack or meal because it can cause a tummy ache for a few short minutes, But, that's not pleasant. Eat a banana or a smoothie with your niacin and then go do something that opens your pores. Basketball and aerobic exercise is ideal - the body is pumping, sweating, and cleaning toxins through the skin. Perfect!
You ideally want to flush within 20 minutes of taking niacin. this indicates that your digestion is good, and quick, and that your blood is cleansing. If you do not feel a flush or it takes a hour or two to feel it, then it has more toxins than niacin, and you want to increase the dose, slowly each day.
I have written about the naicin in detail in my 10-Steps To Detoxification book. If you are interested in learning more about the natural supplements that aid in detoxification, you might want to read my book.