Where do you draw the line between a healthy dose of natural vitamin d and skin cancer risk?

Don't burn: There's no perfect answer. It depends on your risk factors for developing skin cancer. There are also many sources of vitamin d other than the sun including some vegetables as well as vitamin supplements. The main thing is, don't intentionally go out to get a suntan, and don't burn. You will produce vitamin d even if you wear some sunscreen.

In the shade: Unfortunately, there is no guaranteed safe dose for sun exposure. Fair skinned people are especially prone to skin cancer. Vitamin d is safer taken by mouth. Wear sunscreen and a hat when outdoors.

Don't worry: If you spend time outside, and don't live in alaska, canada, etc, chances are good you will get enough vitamin d. You can still make vit d when wearing sunscreen. Go outside, have fun, use skin protection, and vitamin d will not likely be a problem. If you have problems or concerns, you can get a level checked.