Testosterone deficiency: symptoms and thresholds
Testosterone deficiency (TDS / "low T" / andropause) is diagnosed by symptoms plus blood tests together — never bloods alone, never symptoms alone.
The symptom cluster
- Reduced sex drive and morning erections
- Fatigue that sleep doesn't fix
- Low mood, irritability, brain fog
- Loss of muscle despite training; increased body fat (especially around the middle)
- Poor concentration and memory
- Reduced beard growth; less sweating during exercise
- Osteopenia on a DEXA scan in longer-term cases
The numbers
- Diagnosis is considered at total testosterone below 12 nmol/L alongside symptoms (BSSM-aligned assessment threshold); treatment is usually offered below ~8–10 nmol/L, and many NHS labs use local ranges in the 8–12 band before acting.
- Above 12 nmol/L with symptoms, good practice is to look for other causes (sleep apnoea, thyroid, depression, overtraining, alcohol) — because TRT is not the answer to every low-energy state.
What mimics low T (the misdiagnosis engine)
- Obstructive sleep apnoea — fatigue + low morning T that resolves with CPAP.
- Depression/anxiety — overlaps heavily with the mood symptoms.
- Overtraining/under-eating — suppresses T temporarily.
- Alcohol and opioids — both suppress the HPG axis.
The diagnosis sequence (what to expect)
- Symptom questionnaire (AIM-65/ANDROTEST-style tools) at the GP or clinic.
- Two morning total-T tests (varies day to day — one test is not enough).
- LH/FSH + SHBG to distinguish primary (testicular) from secondary (pituitary) causes.
- Prolactin (rules out pituitary causes), PSA + haematocrit (safety before starting treatment).
Where to go
Read how to get TRT in the UK for the NHS vs private decision, and the clinic directory for verified providers. If you have symptoms, start with your GP — the NHS route is free and safe to walk first even if you later go private.
Sources: BSSM position statement (PMCID PMC10307648); NHS pages; clinic published pages verified 2026-10-08.
Affiliate disclosure: Some pages contain affiliate or advertising links, marked with 'sponsored'. Listings are never sold ranking — featured status is labelled on the page. Clinic data is published free regardless of commercial relationships.
Information directory — medically reviewed sources cited per page · Source-checked 2026-10-09 · Independent information directory — not medical advice.