Medical Technology Council Clarifies: Plain Water Is Safe Before Blood Tests, Recommends Healthcare Facilities Update Instructions

The Medical Technology Council has issued academic guidance clarifying that plain water can be consumed normally before blood draws, contradicting some healthcare facilities' instructions to fast from both food and water. The council is communicating this clarification to its members, the general public, and relevant healthcare workers due to widespread misunderstandings that plain water should be avoided like other foods and beverages.

The council clarified that plain water—defined as pure water with no color, taste, calories, or additives—does not affect laboratory test results that require clinical fasting conditions. Conversely, avoiding water provides no benefit and may negatively impact test results. Water deprivation can cause blood concentration, leading to artificially elevated values for hemoglobin, creatinine, and BUN. It also makes blood draws more difficult and increases discomfort and risk to patients.

Additionally, laboratory reference values are typically established under fasting conditions while allowing plain water consumption. Avoiding water may cause results to deviate from these standards. The Medical Technology Council is requesting that healthcare facilities update their pre-test instructions to read: "Avoid all food and beverages except plain water, which may be consumed normally." Proper communication before testing is essential for ensuring quality laboratory results and patient safety.