My homocysteine level was 15. blood test said it was high bc range went up to 12. is a 15 dangerous?

No: Not dangerous, just one of many risk factors for developing coronary disease at a later time. Try to improve the risk factors you can with a healthy diet, not smoking, knowing you cholesterol, and treating if needed, and maintaining a healthy weight. Do not smoke! Homocysteine levels can be lowered with certain b vitamins, but the benefit of this treatment is uncertain.