I started taking 1000mg of vitamin b12 today. how long does it take to show improvement if im deficient?

Were you tested to see if you are B12 deficient? Or were you examined by a Physician to determine B12 deficiency? Or have you consulted with a Nutritionist? Self diagnosis can be dangerous.

You are likely taking 1000 micrograms not mg. The daily need is about 5 micrograms/day. If you can absorb B12, it should get corrected in a day or so. If you do not know if you are deficient, through laboratory testing, you may not wish to keep taking it. For healthy diet: http://www.choosemyplate.gov/., exercise 30 minutes/day, drink enough water daily so your urine is mostly colorless.