Hello again You can do vit D levels in blood. Symptoms of vitamin D deficiency include Bowing of legs,pot belly abdomen,excessive crying Bone pain and muscle weakness. However, for many people, the symptoms are subtle. Yet even without symptoms, too little vitamin D can pose health risks. She may need high dose of vitamin D with calcium supplement so that rickets can be cured. Hope this answers your query. If you have additional questions or follow up queries then please do not hesitate in writing to us. I will be happy to answer your queries. Wishing you good health. Take care.