Alfacalcitol works best between 4 and 24 hours after taking the drug, which is used to treat abnormal vitamin D metabolism, and should be used as directed by a doctor. Alfacalcitol is commonly available in tablet and capsule form. Alfacalcitol tablets instructions pointed out that this product after taking 4~24 hours can reach the peak blood concentration, alfacalcitol capsules after taking the peak blood concentration for 8~24 hours, so between 4~24 hours after taking the drug is the best time for the drug to play a role. Alfacalcitol is an active metabolite of vitamin D3, which is used to improve the symptoms of hypoparathyroidism, chronic renal insufficiency, osteochondritis dissecans, anti-vitamin D rickets patients due to abnormal vitamin D metabolism such as convulsions, hypocalcemia, bone pain, bone damage, and also to treat osteoporosis. Adverse effects of this product include loss of appetite, bloating, diarrhea, thirst, stomach pain, nausea, vomiting, constipation, mild elevation of transaminases. The drug is contraindicated in patients with hypercalcemia, and should be used reasonably under the guidance of a doctor.