Low libido is rarely caused by one thing, which is why there’s no single fix. It typically involves a combination of hormonal shifts, brain chemistry, sleep, stress, medications, and relationship dynamics. The good news is that most of these factors are identifiable and many are reversible. Here’s what’s actually going on when your sex drive disappears, and what you can do about it.
What’s Happening in Your Brain
Sexual desire runs on a push-and-pull system in your brain. One set of chemical signals accelerates desire, and another set acts as the brakes. Dopamine is the primary accelerator. It drives arousal through reward and motivation circuits. Serotonin does the opposite: it signals satisfaction and fullness, essentially telling your brain “you’ve had enough.” Norepinephrine and oxytocin also push desire forward, while your brain’s own opioid and endocannabinoid signals can dampen it.
When this system falls out of balance, with too much braking and not enough acceleration, desire drops. The leading theory behind clinically low libido is that serotonin activity becomes overactive, which suppresses dopamine release and quiets the arousal system. This isn’t just academic. It explains why certain medications tank your sex drive (more on that below) and why strategies that boost dopamine or reduce excess serotonin signaling can help restore it.
Hormones That Drive Desire
Testosterone matters for libido in everyone, not just men. In women under 50, a total testosterone level below 25 ng/dL can indicate androgen deficiency. For women over 50, that threshold drops to 20 ng/dL. Men experience a more gradual testosterone decline starting around age 30, losing roughly 1% per year, and symptoms of low desire often appear when levels fall below the normal range for their age.
Estrogen plays a role too, particularly for women during perimenopause and menopause. Declining estrogen can reduce blood flow to genital tissue, cause vaginal dryness, and make sex uncomfortable, which naturally erodes desire over time. Thyroid hormones, prolactin, and cortisol (your stress hormone) also influence the system. If your libido dropped suddenly or has been low for months, a blood panel checking these levels is a reasonable starting point.
Sleep Is More Important Than You Think
Sleep deprivation directly lowers testosterone. A meta-analysis of studies on healthy men found that going without sleep for 24 hours produced a statistically significant drop in testosterone levels. Staying awake for 40 to 48 hours made the decline even steeper. Partial sleep restriction over several nights showed a smaller, less consistent effect, but the pattern is clear: the less you sleep, the more your hormonal foundation for desire erodes.
Beyond hormones, poor sleep increases cortisol, blunts dopamine sensitivity, and leaves you too tired to feel interested in anything, let alone sex. If you’re consistently getting fewer than seven hours, improving your sleep may do more for your libido than any supplement or medication. Prioritize a consistent wake time, limit screens in the hour before bed, and keep your room cool and dark.
Exercise as a Libido Reset
Physical activity affects nearly every hormone involved in sexual desire: cortisol, estrogen, testosterone, prolactin, and oxytocin. Both aerobic exercise and resistance training (using weights, bands, or machines) have been shown to improve sexual function in women. For men, regular exercise improves blood flow, reduces stress hormones, and supports healthy testosterone levels.
The benefit isn’t just long-term. In women taking antidepressants, exercising shortly before sexual activity significantly increased arousal in a clinical trial. This suggests that even a single workout can temporarily shift your brain chemistry in a direction that favors desire. You don’t need an extreme routine. Three to four sessions per week of moderate-intensity exercise, mixing cardio with some form of strength training, is a solid starting point.
When Medications Are the Problem
SSRIs and other serotonin-boosting antidepressants are one of the most common causes of lost libido. This makes sense given the brain chemistry: these drugs increase serotonin, which suppresses the dopamine-driven arousal system. If your sex drive vanished after starting an antidepressant, you’re not imagining it.
The least disruptive approach is a dose reduction, since sexual side effects are often dose-dependent. If that’s not enough, adding bupropion (which works on dopamine rather than serotonin) has the strongest clinical evidence for reversing antidepressant-related sexual dysfunction across desire, arousal, and orgasm in both men and women. Some doctors may also consider switching to an antidepressant with a lower sexual side-effect profile. Bupropion, mirtazapine, and agomelatine, when used as the primary antidepressant, show little to no effect on sexual function compared to placebo.
Birth control pills, blood pressure medications, antihistamines, and opioids can also lower libido. If you suspect a medication is involved, don’t stop taking it on your own. Talk to your prescriber about alternatives or adjustments.
Stress, Relationship Quality, and Mental Health
Chronic stress keeps cortisol elevated, which directly suppresses reproductive hormones. But stress also hijacks your brain’s reward circuitry, making pleasurable activities feel less appealing. Depression and anxiety create a similar effect, reducing dopamine activity in the circuits that generate wanting and motivation.
Relationship dynamics matter just as much. Unresolved conflict, feeling emotionally disconnected, or a lack of trust can shut down desire even when everything else is working fine. A clinical diagnosis of low sexual desire specifically excludes cases where the root cause is severe relationship distress. In other words, if the relationship itself is the issue, that’s what needs attention first. Couples therapy or individual therapy focused on the relationship can be more effective than any medical treatment in these situations.
Supplements That Have Evidence
Most “libido-boosting” supplements have weak or nonexistent evidence behind them. Maca root is one exception. In a randomized, double-blind, placebo-controlled trial, men with symptoms of age-related hormonal decline took approximately 2 grams of maca three times daily (about 5 to 6 grams total per day) for 12 weeks. At the four-week mark, both the maca group and the placebo group showed improvement. But at 12 weeks, only the maca group maintained significant gains, while the placebo group’s improvement faded. This suggests maca requires consistent use over several months to produce a real effect beyond placebo.
Maca appears to be well-tolerated, but it’s not a hormonal therapy. It doesn’t raise testosterone levels directly. Its mechanism isn’t fully understood, and it’s not a substitute for addressing the underlying causes of low desire.
Prescription Options
For women with persistently low desire that causes distress and isn’t explained by another condition, relationship problems, or medication side effects, there is an FDA-approved option: flibanserin, taken as a daily pill at bedtime. It works on the serotonin-dopamine balance, reducing serotonin’s inhibitory effect on arousal circuits. The most common side effects are dizziness, sleepiness, nausea, and fatigue. It’s not a quick fix. It requires daily use and the effects build gradually.
For men, testosterone replacement therapy is an option when blood tests confirm low levels. It can be delivered through gels, patches, or injections. The benefits for desire are typically noticeable within a few weeks, though full effects may take several months.
A Practical Starting Point
If you’re trying to figure out where to begin, focus on the most common and correctable causes first. Get your sleep to at least seven hours consistently. Start exercising if you aren’t already. Review any medications you’re taking with your doctor. Reduce alcohol, which suppresses arousal and disrupts sleep. If stress or relationship tension is a factor, address it directly rather than working around it.
If those changes don’t help after a couple of months, get bloodwork done. Ask for testosterone (total and free), thyroid hormones, and prolactin at a minimum. A clinical diagnosis of low sexual desire requires that symptoms have persisted for roughly six months and cause real personal distress, so don’t feel like you need to wait for a crisis before seeking help. But do give lifestyle changes enough time to work before assuming something is medically wrong.