Blood tests: which ones to do and how often?

Nov 20, 2025
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Blood tests are a fundamental tool for monitoring general health and preventing the onset of diseases. But which are the most important tests to perform, and how often? In this comprehensive guide, you'll discover everything you need to know about routine blood tests.

Table of Contents

  1. Why do blood tests?
  2. Routine blood tests: what are they?
  3. Complete blood count
  4. Glycemia and metabolic profile
  5. Lipid profile (cholesterol and triglycerides)
  6. Liver and kidney function
  7. Thyroid tests
  8. How often should blood tests be done?
  9. How to prepare for blood tests
  10. Conclusions

1. Why do blood tests?

Blood tests are essential for:

  • Prevention : Identify changes early before symptoms appear
  • Monitoring : monitor the progress of chronic diseases (diabetes, hypertension, dyslipidemia)
  • Diagnosis : Identifying the cause of specific symptoms
  • General assessment : check the correct functioning of vital organs

Regular blood tests allow for timely intervention and healthier lifestyle choices.

Types of blood test tubes

2. Routine blood tests: what are they?

Basic blood tests include:

  • Complete blood count
  • Blood sugar
  • Lipid profile (total cholesterol, HDL, LDL, triglycerides)
  • Transaminases (GOT/AST, GPT/ALT)
  • Creatinine and azotemia
  • Thyroid tests (TSH, FT3, FT4)
  • ESR and CRP (indexes of inflammation)

3. Complete blood count

The complete blood count (or blood count test) analyses:

  • Red blood cells : carry oxygen; low values ​​indicate anemia
  • White blood cells : defend against infections; alterations may signal infections or immune disorders
  • Platelets : essential for coagulation
  • Hemoglobin and hematocrit : indicators of tissue oxygenation

When to do it : annually or in the presence of tiredness, paleness, frequent infections.

4. Glycemia and metabolic profile

Blood glucose measures the level of sugar in the blood:

  • Normal fasting values : 70-100 mg/dL
  • Prediabetes : 100-125 mg/dL
  • Diabetes : ≥126 mg/dL

Glycated hemoglobin (HbA1c) provides an average of blood sugar levels over the last 2-3 months and is essential for those with diabetes.

When to do it :

  • Annually for healthy adults
  • Every 3-6 months for diabetics or prediabetics

5. Lipid profile (cholesterol and triglycerides)

The lipid profile evaluates:

  • Total cholesterol : should be <200 mg/dL
  • LDL ("bad") cholesterol : <100 mg/dL (optimal)
  • HDL ("good") cholesterol : >40 mg/dL men, >50 mg/dL women
  • Triglycerides : <150 mg/dL

High values ​​increase cardiovascular risk.

When to do it : Every 1-2 years after age 40; more frequently if there are risk factors.

6. Liver and kidney function

Liver (transaminases):

  • GOT/AST and GPT/ALT : enzymes that indicate liver health
  • Gamma-GT : sensitive to alcohol and drugs
  • Bilirubin : evaluates bile function

Kidneys :

  • Creatinine : waste product filtered by the kidneys
  • Azotemia (urea) : indicates renal efficiency
  • eGFR : estimated glomerular filtration rate

When to do it : annually, more often if you take medications or have chronic conditions.

7. Thyroid tests

The thyroid regulates metabolism, energy and body temperature:

  • TSH : thyroid stimulating hormone
  • FT3 and FT4 : free thyroid hormones

Alterations can cause hypothyroidism (tiredness, weight gain) or hyperthyroidism (nervousness, weight loss).

When to do it : every 1-2 years, more frequently if symptoms or a family history exist.

8. How often should blood tests be done?

  • Healthy adults (20-40 years) : every 1-2 years
  • Adults over 40 : annually
  • People with chronic conditions : every 3-6 months or as directed by a doctor
  • Pregnant women : according to obstetric protocol
  • Smokers, overweight, family history : more frequent checks

9. How to prepare for blood tests

For accurate results:

  • ✅ Fasting : 8-12 hours (only water allowed)
  • ✅ Avoid alcohol : 24-48 hours before
  • ✅ Do not smoke : at least 2 hours before
  • ✅ Avoid intense physical effort : the day before
  • ✅ Report any medications you are taking : some can alter the results
  • ✅ Hydration : drinking water facilitates blood collection

10. Conclusions

Blood tests are a valuable ally for your health. Regular check-ups allow you to:

  • Prevent diseases
  • Monitor existing conditions
  • Adopt healthier lifestyles
  • Intervene promptly

Remember : tests should always be interpreted by your doctor, who will evaluate the results in the context of your medical history.

Need advice about your blood tests? Always consult your doctor or pharmacist for a personalized interpretation of your results.