Which blood tests to take

Choose supplements from lab results, not guesswork. The core list:

• Complete blood count and ferritin — anaemia and iron stores (especially women, vegetarians, endurance athletes).
• 25(OH)D — vitamin D.
• B12 — vegetarians, people over 50, and those on metformin or antacids.
• TSH — thyroid (tiredness, weight change, feeling cold).
• Glucose / HbA1c and lipids — over 35 or overweight.

In the morning, fasting, once a year. Show the results to a doctor — then I'll match the product and dose.