I took 2 tablets twice a day for 3-5 years, I've only recently swapped to a multi magnesium supplement in the last two months and this one served me well. I know my levels were about right as when I used magnesium oil, I didn't feel any tickling sensation where I'd applied the oil plus blood tests showed I had optimal magnesium intake and this wasn't an NHS test but a full private blood work panel and so I know my absorption and the supplement was working. I do think biocare are trust worthy, clean and good quality products so I am very happy to say I'd recommend this product to anyone.