In nursing, objective data is any information you can gather through observation and testing. It's information you can see, hear, smell or otherwise observe for yourself. Subjective data, on the other hand, is information that comes from the patient and includes symptoms and any information the patient tells you.
Use of Objective Data
Objective data is particularly important when treating a patient because it provides important clues as to what is wrong. Many illnesses can cause a headache or an upset stomach, which are pieces of subjective data the patient supplies. But not all illnesses are accompanied by a fever, rash, elevated blood pressure or other observable, measurable problems. Objective data should always be charted as it is factual information relevant to patient care. Subjective data from the patient, a spouse or visiting friend can be included in the chart but only if the information is helpful or potentially relevant.