Routine Blood Tests for an 18-Year-Old Girl
For a healthy 18-year-old girl without specific risk factors or symptoms, routine blood tests are generally not recommended based on current evidence-based guidelines.
Blood Pressure Screening (Not a Blood Test, But Essential)
- Blood pressure measurement should be performed at every healthcare encounter for individuals 18 years and older 1
- The U.S. Preventive Services Task Force, American Academy of Family Physicians, and American College of Obstetricians and Gynecologists all strongly recommend screening adults age 18 years or older for hypertension 1
- Screen every 2 years if blood pressure is less than 120/80 mm Hg, and annually if systolic blood pressure is 120-139 mm Hg or diastolic blood pressure is 80-90 mm Hg 1
Risk-Based Laboratory Testing
No routine blood tests are universally recommended for healthy 18-year-old girls without specific clinical indications. Laboratory testing should be guided by:
Individual Risk Factors Requiring Specific Testing
- Diabetes screening: Only if the patient has risk factors such as obesity, family history of diabetes, or symptoms of hyperglycemia 1
- Lipid screening: Only if there are cardiovascular risk factors, family history of premature cardiovascular disease, or other metabolic concerns 1
- Complete blood count (CBC): Only indicated if there are symptoms suggesting anemia (fatigue, pallor), infection, bleeding disorders, or other hematologic concerns 2, 3, 4
- Comprehensive metabolic panel (CMP) or basic metabolic panel (BMP): Only indicated when specific clinical variables are present, such as symptoms of liver disease, kidney disease, electrolyte abnormalities, or metabolic disorders 5
Clinical Context Matters
- The complete blood count and metabolic panels are among the most commonly ordered tests, but 10-20% of results are abnormal even in healthy populations 3
- Ordering tests without clinical indication leads to unnecessary follow-up testing, patient anxiety, and healthcare costs 5
- CBC components can predict cardiovascular and metabolic diseases, but this is relevant for symptomatic patients or those with established risk factors, not for routine screening in healthy young adults 6
Important Caveats
- If the patient has specific symptoms, chronic conditions, takes medications, or has a family history of genetic disorders, targeted laboratory testing becomes appropriate 3, 5
- For women of childbearing age, consider discussing reproductive health screening (pregnancy testing if indicated, sexually transmitted infection screening based on sexual history) though these are not "routine" blood tests 1
- Avoid ordering comprehensive panels "just to check" in asymptomatic patients—this practice increases false-positive results and unnecessary interventions 5
What Should Actually Be Done
Focus on the clinical history and physical examination to identify specific indications for testing:
- Document menstrual history, sexual activity, contraceptive use, and reproductive plans 1
- Assess for symptoms of anemia (heavy menstrual bleeding, fatigue, dietary restrictions) 3, 4
- Evaluate lifestyle factors: diet, exercise, substance use, mental health 1
- Screen for cardiovascular risk factors: smoking, obesity, family history of premature heart disease 1
- Only order laboratory tests when specific clinical indicators are present 3, 5