Data collection gathers information needed to make accurate judgments about a patient's present condition. During a health history interview, subjective data is collected from the patient, their caregivers, or family members, and objective data is collected through observations and physical assessment. Patients are the primary source of subjective data. Thus information gathered from patients through interviews, observations, and physical examination is primary data. Secondary sources of data include information obtained from family members, significant others, or interdisciplinary team reports.

Other sources of information pertinent to data collection include medical record information (e.g., patient history, laboratory work, x-ray film results, multidisciplinary consultations) and scientific literature (evidence about assessment techniques and standards).

When preparing for data collection, the nurse identifies the purpose of the nursing assessment (comprehensive, focused, emergency, time-lapsed) and then gathers the appropriate data. The nurse's questions should be purposeful, complete, accurate, factual, and relevant during the patient interview. As much as possible, all the collected patient data should address the patient's health problem and enhance the formulation of the plan of care to maximize the health and well-being of the individual.

Collecting factual and accurate information to avoid misinterpretation is an essential component and consideration in data collection. Along with the aforementioned characteristics, the data obtained should be as relevant as possible. While family members, caregivers, patient records, other health professionals, and literature are sources of data collection, the primary source is a conscious patient alert enough to provide information. Patients with limited mental or communication capabilities, such as young children and older adults with dementia, cannot be relied on to report accurately. The information collected from family and significant others provide secondary data instead of primary data in such cases. It is important to note who provides the patient data in the nursing history to ensure accuracy.

Other sources of patient data include patient health records, relevant literature, interdisciplinary team records, and laboratory and diagnostic reports. Throughout the data-gathering process, clinical nursing skills strengthen the process to ensure the data collected move the patient toward their goal.