PATTAYA, Thailand – The Medical Technologist Council of Thailand has confirmed that patients undergoing blood tests can drink plain water normally before sample collection, stating that it does not affect laboratory results and should not be restricted.
The clarification follows ongoing public confusion over whether patients must avoid both food and water before blood tests. While fasting instructions have long been standard practice, inconsistencies between hospitals have led to mixed guidance, with some facilities advising patients to avoid water entirely.
According to the council’s official statement, published on its Facebook page on April 27, some hospitals have issued instructions that mistakenly group water with food and other beverages under fasting requirements. This has contributed to misunderstandings among patients and healthcare users.
The council emphasized that “plain water”—defined as clear, colorless, calorie-free water with no additives—does not interfere with clinically significant laboratory test conditions that require fasting. On the contrary, it said, avoiding water offers no medical benefit and may even negatively affect test accuracy.
Officials explained that dehydration can lead to hemoconcentration, potentially causing certain laboratory values to appear higher than actual levels. It can also make blood collection more difficult, increasing discomfort and procedural risk for patients.
The council further noted that standard laboratory reference values are based on conditions where patients fast from food but are still allowed to drink water. Extending fasting to include water may therefore introduce inaccuracies in test interpretation.
To address the issue, the council has requested all healthcare facilities to revise patient instructions to a standardized message: “No food or drinks except plain water, which may be consumed normally.”
Authorities stressed that clear communication during the pre-analytical phase is essential to ensuring accurate laboratory results, improving patient safety, and maintaining consistent healthcare standards nationwide. (TNA)
