The NHS definitely does rank highly in the UK. Not sure if it ranks above web md, but they’re usually both in the top 5 results if they have a relevant page.
It pretty much always ranks above WebMD in the UK. WebMD has a very low rank for me. Mayo Clinic is the site that I normally see tussling for the top spot with the NHS. Some examples randomly plucked from my brain:
1. Vitiligo: NHS: 1, Mayo Clinic: 2, WebMD: 7
2. Bronchiolitis: NHS 1, Mayo Clinic 2, WebMD: 9 (on the second page!)
3. Appendicitis: NHS 1, Mayo Clinic 2, WebMD: 3
4. Myopia: Mayo Clinic 1, WebMD 2, NHS: 3
5. Gastroenteritis: NHS Inform (never seen this before?) 1, WebMD: 2, Mayo Clinic 3, NHS: 4
6. Hodgkin's disease: Mayo Clinic 1, NHS: 2, WebMD: 5
1. Vitiligo: NHS: 1, Mayo Clinic: 2, WebMD: 7
2. Bronchiolitis: NHS 1, Mayo Clinic 2, WebMD: 9 (on the second page!)
3. Appendicitis: NHS 1, Mayo Clinic 2, WebMD: 3
4. Myopia: Mayo Clinic 1, WebMD 2, NHS: 3
5. Gastroenteritis: NHS Inform (never seen this before?) 1, WebMD: 2, Mayo Clinic 3, NHS: 4
6. Hodgkin's disease: Mayo Clinic 1, NHS: 2, WebMD: 5