Sleep, mood and hormones: the markers worth measuring

What people notice

• Waking unrefreshed regardless of hours in bed
• Snoring, witnessed pauses in breathing, or waking with a dry mouth and headache
• Afternoon energy collapse
• Low mood, irritability and a short fuse
• Reduced libido and slower recovery from training

Symptoms overlap between causes. This list is a prompt to measure, not a diagnosis.

Markers worth measuring

Morning testosterone (total and free)

Sleep restriction measurably lowers it — a low result in a poor sleeper is often a sleep finding, not a gonadal one.

Morning cortisol and DHEA-S

Chronic sleep debt distorts the daily curve and the cortisol-to-DHEA relationship.

HbA1c, fasting glucose and insulin

Short sleep reduces insulin sensitivity within days; the metabolic markers show whether it is biting.

TSH, free T4, free T3

Thyroid dysfunction is a common and treatable cause of fatigue and low mood that mimics poor sleep.

Ferritin

Low iron stores are strongly associated with restless legs, which fragments sleep without waking you fully.

Vitamin D and B12

Both affect mood and energy and are common, correctable deficiencies.

hs-CRP

Sleep fragmentation and untreated sleep apnoea raise systemic inflammation.

FAQs

Can poor sleep lower testosterone?

Yes, and quickly. Controlled studies show a measurable fall in healthy young men after about a week of restricted sleep.

Should I get a sleep study or a blood test?

If you snore, stop breathing, or wake with headaches, prioritise the sleep study. Bloods complement it; they do not replace it.

Which markers matter most for low mood?

Thyroid function, B12 and folate, vitamin D, ferritin and full blood count are the standard physical exclusions before attributing symptoms to mood alone.

When should the blood be drawn?

Morning, 7am–10am, fasted if the panel includes glucose, insulin or lipids — and ideally not the morning after an unusually bad night, which will skew it.