Not a diagnosis: a head start. These are the three drivers most worth checking first, based on what the evidence says gets missed most often.
Deficiency tracks infection frequency; most of the UK is low half the year.
Under 6 hours measurably blunts immune response. No supplement compensates.
Chronic cortisol suppresses immunity. The illness-after-deadline pattern is real.
Vitamin D, full blood count, HbA1c
1. Start a two-minute note in the free journal that asks back, so the pattern becomes visible.
2. Take the test list above to your GP; the Health Journal will help you say it clearly.
3. Read the evidence: Browse the library.
Want it tracked and reviewed monthly by a real person? The Club, £10/month.
Education, not diagnosis, and never a replacement for your GP or pharmacist. Reference ranges and guidance vary; sudden, severe or worsening symptoms need 111, or 999 in an emergency. By Hussain Sharifi · independent, affiliate-free health intelligence.