"Do I need to fast for this?" is one of the most common questions we hear when we order labs. The short answer: some tests require fasting, most don't, and the rules are simpler than the internet makes them sound. Here's what we tell our own patients in Las Vegas and Henderson.
Which blood tests actually require fasting?
- Fasting glucose, used to screen for diabetes and prediabetes. Fast 8–12 hours.
- Lipid panel (cholesterol), guidelines now allow non-fasting for most adults, but we often still ask for a 9–12 hour fast so your triglycerides read accurately.
- Basic or comprehensive metabolic panel, the glucose component reads higher after eating, so an 8-hour fast is standard.
- Insulin level, always fasting, usually 8 hours.
Tests that do not require fasting include A1c, thyroid (TSH), CBC, vitamin D, B12, and most hormone panels. If you're ever unsure, ask us when we order the labs.
How long do you have to fast before blood work?
Eight to twelve hours is the standard window. The easiest approach: schedule a morning draw, stop eating after dinner the night before, and skip breakfast. Coffee and food both count as breaking the fast.
What can you drink while fasting?
- Water, yes. Please drink it. Hydrated veins are easier to draw.
- Black coffee or plain tea, technically yes, but caffeine can nudge some readings, so we suggest water only when possible.
- Juice, soda, cream, sugar, no. Anything with calories breaks the fast.
Should you take your morning medications?
In most cases, yes, take them with water as usual. There are exceptions for certain diabetes medications (taking them without eating can drop your blood sugar), so confirm with us the day before if you take medication for diabetes.
Where to get fasting labs in Las Vegas and Henderson
We order labs as part of annual physicals, diabetes care, and most new-patient visits, and the draw stations our patients use are within about 10 minutes of our office at Sunset and Fort Apache. If you're establishing care and want labs done right, request a call back and we'll get you scheduled.