My "not-custom" multivitamin tables ("Immunace extra protection") contain 150 mg (see the other ingredients on their website, it also contains selenium (180 μg selenium, 1000 μg copper, 15 μg zinc and lots of other stuff, like bioflavonoids, betacarotene, etc). Not that exteme dosages, but still ok. I might take some 500 g Vitamin C tablets twice a day to go with the Immunace. I don't know exactly..