Most of the biological, biochemical, pharmaceutical and toxicological studies of ytterbium were performed in small animals, such as mice. The oral administration of ytterbium compounds has a very limited effect, once very little ytterbium is absorbed by the body. The subcutaneous injection provides a larger absorption, but the excretion of the element is rather slow. About 25% of the absorbed ytterbium is deposited in the liver and 65% in the bones, being the stockings lives respectively of about 15 days and 2,5 years. The rare earths, including ytterbium, have very little acute toxicity.