Dear sir, does it good to take 1 gram of vitamin d3 every week or for 6 months?

VERY DANGEROUS!!!: 1 gram of Vit D=1 million micrograms=40 million iu of Vit D. An dose over 40,000 iu/day may be toxic so 1 gram a week would be 143 times the toxic dose! As you can see, you don't need a whole lot of Vit D. Most people need to take 5,000-8,000 iu/day on a regular basis to maintain optimal levels (8000 iu is 200 mcg, which is only .0002 grams a day. Adequate sun can also provide Vit D. Only take D3.