* Lipid Panel (Cholesterol): This is the most common reason for fasting before a blood draw. Eating affects cholesterol and triglyceride levels.
* Glucose (Fasting Blood Sugar): Crucial for diagnosing diabetes and prediabetes. Food intake dramatically alters blood glucose levels.
* Triglycerides: These fats are highly sensitive to recent food consumption.
* Insulin: Similar to glucose, insulin levels fluctuate significantly after eating.
* Some liver function tests: While not all, some aspects of liver function testing may be impacted by recent food intake.
* Gastrin: This hormone is directly affected by food intake.
* C-Peptide: This test is used to assess insulin production and secretion.
Important Note: It's crucial to always confirm with your doctor or the lab which tests require fasting. They will provide specific instructions based on the ordered tests and your individual health situation. Failing to fast when required can lead to inaccurate results and potentially incorrect diagnoses or treatment plans. They might also tell you what you *can* drink (usually water only) during your fast.