Low libido

Start with when it changed

One question first, and be as precise as you can.

When did it change? Not roughly. What season, what year, and what else was happening then.

Because the single most useful thing about this symptom is that it usually has a date, and the date usually has something next to it.

A new medication. A new baby. A job that started eating your sleep. A period of illness. A contraceptive started or stopped. A stretch of eating badly and training too hard.

Write down the month it changed and everything you can remember about it. That list finds the cause more often than any panel.

And if the honest answer is that it was gradual over years with nothing alongside it, that points somewhere different and it is worth knowing that too.

Why nobody has found it yet

Here is the tension though.

This symptom sits in a gap between specialties, and it falls through it regularly.

Bring it to a GP and you may get a testosterone test if you are a man and a conversation about stress if you are a woman. Bring it to a therapist and the physical variables often go unexamined. Bring it nowhere, which is what most people do, and nothing gets checked at all.

There are two specific gaps I would name.

The first is medication. SSRIs affect desire, arousal and orgasm, and this is well recognised. Yet people frequently do not mention it, sometimes out of embarrassment and sometimes because they assume it is the price of feeling better. It often is not, because dose adjustments and alternative options exist. That conversation is worth having.

The second is women and testosterone. Testosterone matters for libido in women too, and it is measured far less often than in men. Someone can go through an entire workup without anyone checking the hormone most directly tied to what they came in about.

Neither of those gaps is about a rare condition. Both are about a question that did not get asked.

The causes, and what separates each

Read this as a map rather than a diagnosis. Two or three of these commonly run together.

Medications. SSRIs and SNRIs most notably, plus some blood pressure medications, finasteride, and hormonal contraceptives, which lower free testosterone by raising SHBG. Distinguishing sign: the change tracks a prescription start or change. Move: raise it with your prescriber, never stop on your own.

Chronic short sleep. Lowers testosterone and drives the fatigue and low mood that independently reduce desire. Distinguishing sign: you are averaging under seven hours. Free to test and the largest unclaimed lever for many people.

Thyroid, in either direction. Affects energy, mood and sex hormone binding globulin. Distinguishing markers: a full thyroid panel with free T3, free T4 and antibodies.

Low iron stores. Contributes through fatigue, and is worth ruling out particularly in women with heavy periods. Distinguishing marker: ferritin with hs-CRP, since stores empty before hemoglobin falls.

Sex hormones. For men, total and free testosterone with SHBG, drawn in the morning. For women, testosterone and SHBG alongside estradiol and progesterone, timed to the cycle where relevant.

Perimenopause and menopause. Changes in oestrogen affect desire, arousal and comfort, and the last of those is treatable in ways many women are never told about. Worth raising with a doctor directly.

Mood, stress and the relationship itself. Depression reduces desire directly, chronic stress does too, and relationship strain is a real cause rather than a polite deflection. None of these are lesser explanations and all deserve proper attention.

The thing that is free and nobody tries

Alright. Before any hormone panel, there is something worth knowing about sleep, because the effect is larger than its reputation.

Testosterone is largely produced during sleep, particularly in the deeper stages. Cut sleep and you cut production. That is not a wellness claim, it is straightforward endocrinology.

The 2021 randomised double-blind crossover study I keep coming back to is instructive here for a different reason than usual. Thirty-four healthy young men, four nights at four hours of sleep, and the researchers specifically clamped cortisol and testosterone in one arm because sleep loss is known to raise the first and lower the second.

That is the assumption the study was built on, stated in its own opening line: sleep loss in men increases cortisol and decreases testosterone.

What the study went on to show is that fixing those two hormones cut the resulting insulin resistance roughly in half, which tells you how much of the metabolic damage of short sleep runs through exactly that hormonal shift.

So here is the practical consequence for this page. If you are sleeping six hours and about to spend money on a testosterone panel, you may end up measuring your sleep debt and calling it your hormone level.

Fix the sleep first, for four to six weeks, then test. The number you get will actually be about you rather than about your schedule.

Where the honest hedge goes

I am not a doctor and I am not diagnosing anyone.

I want to be careful about testosterone specifically, because it is heavily marketed and the relationship between levels and libido is looser than the advertising implies. Plenty of men with lower-range testosterone have normal desire, and plenty with mid-range levels do not. That is why a good clinician reads levels alongside symptoms rather than treating a number. Testosterone therapy is a genuine medical decision with real trade-offs including fertility, and it belongs with a physician rather than a clinic that advertises.

I also want to say plainly that not every cause here is biochemical, and treating the psychological and relational explanations as second-tier does people a disservice. Depression reduces desire directly. So does a relationship that is not working. Those are not the consolation prize when the labs come back clear, they are causes in their own right and they respond to proper support.

Some presentations need a doctor rather than a panel. Sudden change, erectile difficulty, breast tissue changes, loss of body hair, or visual changes with headaches all warrant assessment, since the last combination in particular can point at a pituitary problem.

And if low mood is a significant part of this, that deserves care for itself. In the US you can call or text 988 for the Suicide and Crisis Lifeline, any hour.

I am not saying your hormones are the answer. I am saying they are variables, and so is your prescription list, and so is your sleep, and most people check none of the three.

So. Here is what I would actually do.

Tonight, at no cost. Write down the month it changed and what else was happening then. That single list solves this more often than any test.

Also tonight. Read your medication list against that date. If an SSRI or a contraceptive lines up, that is your first conversation, and it is a conversation rather than a decision to make alone.

Then fix the sleep before you buy the panel. Four to six weeks at seven and a half hours, and then test. Otherwise you risk measuring your schedule.

When you test, go wide once. A full thyroid panel, ferritin with hs-CRP, and vitamin D3.

Add the hormones appropriate to you. Men: total and free testosterone with SHBG, morning draw. Women: the same two alongside estradiol and progesterone, timed with a provider.

Do not treat the relational and emotional side as the leftover. If it belongs there, it belongs there properly, with real support.

The bigger project. Take the results to a good functional medicine doctor who reads the whole picture rather than one number.

None of this has to happen this week. But tonight you can write down the month it changed.

You are not broken and you have not simply aged out of yourself. You are a system where desire sits downstream of sleep, thyroid, iron, mood and a prescription list, and any one of those can quietly turn the volume down.

Your body is not broken. It is blocked. And often the block has a date on it, and something written next to that date that nobody thought to connect.

Go find the month it changed.