Libido and your blood

Sexual desire is multifactorial. How things are going in your relationship, how much stress you experience, how you sleep, which medication you use and how you feel often weigh more heavily than a blood value. A blood test only reveals the physical part: hormones such as testosterone, thyroid function and the body's iron stores.

That makes the outcome useful in two ways. An abnormal value can fit your symptoms, but does not automatically explain them; context determines what the result means. And a normal result does not rule out everything, but it does help: you then know the most obvious measurable factors have become unlikely, and you can look at the rest with more focus.

In men, a low testosterone can be associated with reduced sexual desire, often together with fatigue, low mood or less energy during exercise. A single complaint on its own says little; it is the combination of symptoms that makes measuring worthwhile.

The result strongly depends on context. Testosterone is highest in the morning and falls during the day; a morning blood draw is therefore preferred. Lack of sleep, illness, significant overweight and some medicines can also temporarily lower the value. A single lower value is therefore not a diagnosis; in the written explanation our doctor weighs whether a re-test makes sense.

The thyroid and the iron stores usually do not influence libido directly, but via energy. A slow thyroid can show as fatigue, feeling cold, weight gain and low mood; reduced interest in sex can fit that picture. TSH is the first measurement to assess thyroid function.

Ferritin reflects the body's iron stores. An iron deficiency can be associated with persistent tiredness, and someone who is tired for a long time often has less desire as well. If something turns up on this route, you are not treating the libido itself but an underlying factor that can contribute to it.

A normal result is a real answer: a physical cause in hormones, thyroid or iron has then become unlikely. Attention shifts to the factors that do not show in blood. Think of prolonged stress or worrying, too little sleep, alcohol, and how things are between you and your partner.

Also take a critical look at medication. Some antidepressants, among others, are known to be able to dampen sexual desire. Never stop a medicine on your own, but discuss with your GP whether there are alternatives. A recent, doctor-reviewed result is a useful starting point in that conversation.

Blood testing without a referral is meant to give insight. You choose which values are measured, you arrange the request online and you receive your result with an explanation from a BIG-registered doctor. That way you map the physical side of your symptoms: testosterone, thyroid function and iron stores, in a single draw.