Blood Tests
A blood test is one of the most informative diagnostic tools in medicine. A single vial can reveal your cholesterol, blood sugar, organ function, immune status, and much more. These guides help you understand what each test measures, what normal ranges look like, and how to prepare for accurate results.
How to Prepare for a Blood Test: Complete Checklist
Exactly how to prepare for a blood test — fasting rules, medications, hydration, and day-of tips to ensure accurate results. Printable checklist included.
- ✓ Fasting 8–12 hours is required for glucose and lipid panels but not for most other tests
- ✓ Drink 2–3 glasses of water before your appointment — good hydration makes veins easier to access
- ✓ Bring a complete medication and supplement list; some drugs must be paused before testing
Blood Test Normal Ranges Chart: Complete Reference Guide
Complete blood test normal ranges chart covering CBC, cholesterol, glucose, kidney, liver, thyroid, and 50+ common lab values. Updated reference ranges for adults.
- ✓ Reference ranges cover 95% of healthy people — 5% of healthy individuals will show values outside range without disease
- ✓ Ranges differ between men and women, and change with age — context always matters
- ✓ Three types of 'normal' exist: lab statistical range, population optimum, and your personal baseline
Cholesterol Levels Chart by Age: LDL, HDL, and Triglycerides Explained
Complete cholesterol levels chart by age and sex — LDL, HDL, total cholesterol, and triglycerides. Learn what your numbers mean and when to take action.
- ✓ Total cholesterol below 200 mg/dL is desirable; 240 mg/dL or higher is high risk
- ✓ LDL ('bad' cholesterol) below 100 mg/dL is optimal; 160 mg/dL or higher is high risk
- ✓ HDL ('good' cholesterol) above 60 mg/dL is protective; below 40 mg/dL raises heart disease risk
What Tests Are Done on Donated Blood? FDA's 5-Layer Safety System
Learn what tests are performed on donated blood in the US — 11-12 mandatory screenings, the FDA's 5-layer safety system, and how the blood supply is protected.
- ✓ Every unit of donated blood in the US undergoes 11-12 mandatory tests before it can be used
- ✓ The FDA's blood safety system has 5 layers: donor screening, blood testing, donor deferral lists, quarantine, and investigation
- ✓ Tests screen for HIV-1, HIV-2, hepatitis B, hepatitis C, HTLV-1, HTLV-2, syphilis, and blood group compatibility
Understanding Blood Test Results: A Complete Guide
Learn how to understand blood test results, what common tests measure, and what normal vs. abnormal values mean for your health. 150+ tests explained.
- ✓ Blood tests are a primary diagnostic tool — a snapshot of your health at the time of testing
- ✓ Reference ranges are based on 95% of healthy people, so 5% of healthy individuals may fall outside normal without any problem
- ✓ Many non-illness factors affect results: fasting status, medications, stress, sleep, and physical activity