Low energy, flat mood, no drive. That symptom list is the entire marketing basis of the testosterone industry, and it is also the symptom list of about six other things. The trial that tested the claim directly is the one nobody quotes.
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See a doctor within a few weeks if low mood, anxiety, or loss of interest has lasted more than two weeks, or is affecting work, sleep, or relationships.
A routine visit is fine to raise a mood change that is mild or clearly tied to a specific stressor.
Who to see: a primary care doctor is a reasonable start and can refer you to a therapist or psychiatrist; if a medication is a suspected cause, do not stop it without talking to whoever prescribed it first.
Worth asking: whether a symptom you have been attributing to something else (a medication, low testosterone, general stress) might actually be a mood issue worth treating on its own.
In the Testosterone Trials, 790 men aged 65 and over, the trial specifically designed to test vitality did not improve fatigue or low energy. The trial designed to test physical function did not improve walking ability. The one that clearly worked was sexual function. When all the trial data were pooled there was some signal for mood and depressive symptoms, but the trial built to answer the energy question answered it negatively. If you are tired and flat with a normal testosterone level, testosterone is not the lever.
| Trial population | 790 men aged 65 and over |
|---|---|
| Sexual function trial | Improved: increased sexual desire and activity |
| Vitality trial | Did not improve fatigue or low energy |
| Physical function trial | Did not improve walking ability |
| Pooled data on mood | Some signal for mood and depressive symptoms |
| The trial built to test energy | Answered the question negatively |
| If your testosterone is normal and you are tired | Testosterone is not the lever |
Does testosterone improve mood and energy?
The Testosterone Trials were a coordinated set of randomised trials in 790 men aged 65 and over across twelve US sites, each designed to test a specific outcome rather than to fish across many.
| Trial | Result |
|---|---|
| Sexual function | Improved, increased sexual desire and activity in men with low sexual function |
| Vitality | Did not improve fatigue or low energy |
| Physical function | Did not improve walking ability |
That is close to the inverse of how testosterone is sold. The thing it reliably improved was libido. The things it did not improve were energy and physical capability, which is what the advertising is almost entirely about.
Why does the advertising say otherwise?
Worth being precise about who this applies to. These were men aged 65 and over with low testosterone by proper measurement. They are, if anything, the population most likely to benefit. A negative vitality result in that group is not easily explained away as the wrong patients.
And note what the clinics selling this actually promise. Energy. Focus. Drive. Getting your edge back. The trial that tested exactly that construct (vitality, meaning fatigue and low energy) is the one that came back negative, and it is not the one that appears in the marketing.
None of this means testosterone treatment is useless. For a man with genuinely low testosterone confirmed on two early-morning measurements plus symptoms, it is a legitimate treatment with a real effect on libido and a reasonable cardiovascular safety profile. It means the specific promise of restored energy is not supported by the trial built to test it.
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What did the pooled data actually show?
Being fair to the evidence cuts both ways.
When data from across the Testosterone Trials were pooled, there was some benefit for mood, energy and depressive symptoms, and walking speed and distance also showed improvement. That is a real finding and it should not be buried.
It is also weaker evidence than the individual trials. A pooled analysis across outcomes has more statistical power but less design discipline. The individual trials were built with a pre-specified primary outcome, and when a purpose-built trial says no and a pooled analysis says maybe, the purpose-built trial is the more conservative and more reliable reading.
There is a broader literature suggesting testosterone treatment may reduce depressive symptoms in men, and it is an active research question rather than a settled one. What it does not currently support is treating testosterone as an antidepressant, or as a substitute for assessing depression properly. Exercise, by contrast, has been tested against depression in more than 200 trials.
Why are the symptoms so hard to attribute?
Here is why this matters more than a debate about one trial.
Fatigue, low mood, poor concentration, reduced libido and disturbed sleep are the symptom list for low testosterone. They are also the symptom list for depression, for obstructive sleep apnoea, for thyroid disease, for anaemia, for excessive drinking, and for being a man in his late forties with a demanding job and small children.
A clinic that measures only testosterone will find only testosterone. If the number comes back at the low end, the story closes, and the depression, the sleep apnoea or the drinking goes uninvestigated while a man spends money and injects a hormone that the relevant trial says will not fix his energy.
The reverse error is just as common. A man told his testosterone is “normal” and sent away, with nobody asking what else might explain six months of exhaustion.
Two specific overlaps are worth naming. Depression in men often presents as irritability, withdrawal and drinking rather than sadness, so a man can be genuinely depressed and describe himself as merely tired and short-tempered. And carrying excess weight both lowers testosterone and disrupts sleep, weight loss raises testosterone measurably, by more than any supplement has ever demonstrated.
What should you check first?
If the complaint is low energy and flat mood, a sensible sequence looks like this.
Depression, seriously considered. Not as a formality. It is the most common cause of this symptom set and the one with the best-evidenced treatments.
Sleep. How much, and how good. Snoring and unrefreshing sleep point at obstructive sleep apnoea, which is common in exactly this population and which independently lowers testosterone.
The basics on bloods. Thyroid function, full blood count, glucose or HbA1c, and, yes, a morning testosterone, measured properly.
Alcohol and medications. Both are common, both are reversible, and neither shows up unless someone asks. If you are taking an antidepressant, note that the sexual side effects are far more common than most men are told and are manageable without stopping the drug.
Then testosterone, if the number and the symptoms both support it. Not first, and not alone.
Common questions about testosterone, mood and energy
Will testosterone give me more energy?
The trial built specifically to answer that question found it did not. In the Testosterone Trials, involving 790 men aged 65 and over, the vitality trial did not improve fatigue or low energy, and the physical function trial did not improve walking ability. The one that clearly worked was sexual function.
Does testosterone help depression?
When all the trial data were pooled there was some signal for mood and depressive symptoms, which is a weaker form of evidence than a trial designed to test it. The honest position is a possible modest effect on mood, alongside a clear negative result for energy and fatigue specifically.
Why do clinics advertise testosterone for energy then?
Because tiredness is the most common complaint men present with, and it is the symptom most easily attributed to a hormone. It is also the outcome the trials most clearly failed to move. That gap between what is advertised and what was measured is worth knowing before paying for treatment.
I am tired and flat with normal testosterone. What now?
Testosterone is not the lever, and treating a normal level will not change anything. A more productive order is sleep, including screening for sleep apnoea which is common and under-diagnosed in men; thyroid function; iron studies; alcohol intake; and depression itself, which presents in men as fatigue and irritability far more often than as sadness.
Can low testosterone cause depression?
The symptom lists overlap substantially, which is exactly why attribution is difficult: low mood, fatigue, reduced libido and poor concentration appear in both. That overlap is a reason to check a testosterone level in a man with those symptoms, and also a reason not to assume a low-normal result explains them.
Sources
- Snyder PJ, Bhasin S, Cunningham GR, et al. Effects of testosterone treatment in older men (The Testosterone Trials). New England Journal of Medicine, 2016. New England Journal of Medicine
- Mulhall JP, Trost LW, Brannigan RE, et al. Evaluation and Management of Testosterone Deficiency: AUA Guideline, 2018. AUA guideline
- Walther A, Breidenstein J, Miller R. Association of testosterone treatment with alleviation of depressive symptoms in men: a systematic review and meta-analysis. JAMA Psychiatry, 2019. PubMed
This article is for information only and is not medical advice. It cannot account for your individual circumstances. Talk to a doctor about your own situation, particularly before starting or stopping any prescription medication. If you are struggling with your mental health, please speak to a qualified professional.

