The present invention relates to a simple and convenient process for preparing solid lipid sustained release nanoparticles for delivery of drugs/vitamins, preferably fat soluble vitamins and more specifically Vitamin D3 and retinoic acid (RA). The process involves microemulsion technique. The nanoparticles of Vitamin D3 and RA obtained by the process of the present invention have utility in treatment of diseases like tuberculosis. Use may be extended to other diseases like AMD, diabetic retinopathy, cancers, hyperpigmentation, acne, and osteoporosis.
