Abstract: Many pharmaceuticals require a specific tissue for injection, such as adipose or muscle, to optimize the effect of the drug. This is important to achieve the desired bioavailability of the injected substance. In some cases, intravenous injections are desired over subcutaneous and intramuscular. The invention is a bioimpedance method and apparatus for sensing a hypodermic needle's transition from subcutaneous adipose to muscle tissue. The invention could also be used to sense a vascular transition. The sensing can be integrated into instrumentation that identifies the tissue or simply signals that the transition has occurred. The physician or nurse could then confidently inject the medication into the intended tissue.