Because vitamin D food sources are so limited and there are risks in relying on sunlight for vitamin D (increased risk of skin cancer), a vitamin D supplement may be your best option. Of course, you cannot even make vitamin D in much of the northern United Sates from sunlight from November to April. Current recommended levels for persons aged 9 to 70 years are 600 IU of vitamin D. daily. Many multivitamins contain 600 to 1000 IU of vitamin D. However, depending on your current blood levels, you may need more. Currently the tolerable upper level of supplement and food combined is 4000 IU. However, your don’t want to supplement with higher doses unless you know your current blood vitamin D levels. If you have a severe deficiency, your physician can prescribe a very high weekly dose and recheck levels. In most persons, 1000 IU daily raises levels about 10 ng/dl.