The duration of taking Vitamin D3 chewable tablets depends on your current vitamin D levels, age, and overall health, so it is best determined by your doctor. Generally, they can be taken daily for several weeks to months, with follow-up blood tests to monitor levels and adjust the dose if needed. The tablets are best taken with a meal containing fat, ideally in the morning or early afternoon, to improve absorption and avoid interfering with sleep. Always follow your doctor's advice regarding the dosage and timing.