In Vivo vs. In Vitro: What Are the Differences?

The terms "in vivo" and "in vitro" describe different types of scientific research. "In vivo" means research done on a living organism, while "in vitro" means research done in a laboratory dish or test tube.

Both types of studies are used by medical researchers developing drugs or studying diseases. Each type has benefits and drawbacks. 

In Vivo vs. In Vitro: Definitions

In vitro: The term in vitro comes from the Latin "in glass." It refers to a medical study or experiment that is done in the laboratory within the confines of a test tube or laboratory dish. This means tissue, cells, or other parts of an organism are removed and placed in a laboratory dish. Researchers may use these samples to test the action of a drug or study a disease process.

In vivo: The term in vivo comes from the Latin "in (something) living." It refers to a medical test, experiment, or procedure that is done on (or in) a living organism, such as a laboratory animal or human. 

Clinical trials or medical studies may be performed either in vivo or in vitro. These approaches are similar in that they are both done in order to make advances in the knowledge and treatment of illness and disease as well as understanding "wellness" and normal bodily functions.

But there are also many important differences in how in vivo and in vitro studies are conducted, how they can be interpreted, and the practical applications of any discoveries which are made.

In Vitro Medical Studies

Medical studies (such as looking at the ability of a drug to treat cancer) are often first performed in vitro—either in a test tube or laboratory dish. An example would be growing cancer cells in a dish outside of the body to study them and possible treatments.

Researchers learn as much as possible about a drug before exposing humans to potential negative effects. If a chemotherapy drug, for example, does not work on cancer cells grown in a dish, it would be unethical to have humans use the drug and risk the potential toxicity.

In vitro studies are important in that they allow more rapid development of new treatments—many drugs can be studied at one time (and they can be studied in a large number of samples of cells) and only those that appear to be efficacious go on to human studies.

An absence of biokinetics (how the body transports and metabolized drugs and toxins) is one of the significant drawbacks of in vitro studies. This, as well as several other factors, can make it very difficult to extrapolate the results of in vitro tests. Thus, it's hard to know what might be expected when the drug is used in vivo.

In Vivo Clinical Trials

In contrast to in vitro studies, in vivo studies are needed to see how the body as a whole will respond to a particular substance.

In some cases in vitro studies of a drug will be promising, but subsequent in vivo studies fail to show any efficacy (or, on the other hand, find a drug to be unsafe) when used within the multiple metabolic processes that are continually taking place in the body.

An example of how in vivo studies are needed to evaluate drugs is with respect to drug absorption in the body. A new drug may appear to work in a dish, but not in the human body. It could be that the drug is not absorbed when it passes through the stomach, so it has little effect on humans.

In other cases, even if a drug is given intravenously, the drug might break down through continuous body reactions. Therefore, the drug would not be effective when used directly in humans.

It's important to note that oftentimes in vivo studies are first done in non-human animals such as mice. These studies allow researchers an opportunity to see how a drug works amid other bodily processes.

A Word From Verywell

When you look at studies done to evaluate cancer treatments—or any other treatments—checking to see which kind of study it is (in vivo vs in vitro) is an important first step.

In vitro studies are extremely important and lay the groundwork for further research, but many of these studies declare findings that are interesting—but will not affect you as an individual for quite some time to come.

In contrast, in vivo studies are looking at the actual effect on an organism—whether a laboratory animal or a human.