When a healthcare provider orders a fasting blood test, you must abstain from all food and beverages, except plain water, for a specified period, typically eight to twelve hours. This medical fasting protocol ensures the accuracy of certain diagnostic screenings. While consumption rules are clear, questions often arise about routine personal care activities, like brushing your teeth, which involve substances entering the mouth.
The Direct Answer: Brushing Teeth and Medical Fasting
In most circumstances, brushing your teeth before blood work is permitted, allowing you to maintain basic oral hygiene. The primary concern is preventing the ingestion of any substance that could metabolize and alter your blood chemistry. The simple rule is to brush as you normally would, but ensure you do not swallow the toothpaste or any subsequent rinse water. This guidance also extends to mouthwash. Minute amounts of residue absorbed through the oral mucosa are negligible and will not affect your lab results.
Why Strict Fasting is Required for Blood Tests
Strict fasting is required because consuming calories directly impacts the concentration of certain markers in the bloodstream. When you eat, the digestive system breaks down nutrients, which are absorbed into the blood. This process causes temporary, yet significant, spikes in compounds that the test aims to measure at a baseline level.
A fasting blood glucose test, for example, measures the amount of sugar circulating after a period without food intake to screen for conditions like diabetes. Eating even a small amount of food or drinking a sugary beverage would artificially elevate this glucose level, leading to an inaccurate reading. Similarly, a lipid panel measures triglycerides and cholesterol; consuming fatty foods before the test would temporarily raise triglyceride levels. If the fast is broken, the results become unreliable, necessitating a rescheduled appointment and delaying diagnosis.
Navigating Specific Oral Hygiene Products
The potential for inaccurate results shifts the focus to the ingredients within oral hygiene products. Many toothpastes and mouthwashes contain artificial sweeteners or sugar alcohols, such as sorbitol or xylitol, added for flavor. These ingredients are technically caloric and can be metabolized, potentially stimulating an insulin response if swallowed in large quantities.
To minimize risk, consider using a plain, unflavored toothpaste or simply brushing with water before your test. If using regular toothpaste, use only a pea-sized amount and dedicate extra attention to rinsing and spitting repeatedly. Mouthwashes present an increased risk, especially since some contain alcohol or high concentrations of sweeteners. If you are concerned, a simple rinse with plain water is the safest alternative. Staying hydrated with plain water is encouraged during fasting, as it keeps veins full and makes the blood draw process easier.