Untreated means not having received any medical care, processing, or preparation that would normally be needed. When something is untreated, it remains in its original state, without any intervention to change or improve it.

In medicine, an untreated illness is one that a person hasn't gotten help for yet. An untreated infection might get worse over time, while an untreated broken bone might not heal properly. Doctors worry about untreated conditions because they can lead to bigger problems later.

The word also applies to materials and substances. Untreated wood hasn't been sealed or protected with paint or varnish, so it may eventually rot or splinter if left outside. Untreated water from a lake or river can contain bacteria and particles that could make you sick, which is why cities treat their water before it flows to your tap. Untreated fabric might shrink or fade more easily than treated fabric.

When something is untreated, it means no one has taken the steps to protect it, improve it, or fix it. The word signals that action is usually needed but hasn't happened yet.