The desire to have sex, also known as libido, is one of the body’s many wonderful mysteries. Some call it “instinctual” and a “primitive biological urge” – for others, it’s an “existential need.”

Sex drive differs widely among us, and each of us has a pretty typical pattern, similar to, say, handwriting style.

Think of it as a habit done with a certain rhythm, like eating or breathing. But your libido can vary by day, and even by the hour, regardless of your testosterone levels (unless testosterone levels get very low, which would tank your libido).

When to Evaluate Libido

Low sex drive is most commonly due to stress. The everyday tussle and toil of living in today’s relentless world is a great and constant source of stress.

The way stress affects libido is pretty clear, too. We aren’t that far evolved from the caveman (which we were 100,000 years ago).

Being anxious or worried about pretty much anything puts the nervous system into a primitive “fight-or-flight” response which absolutely buries sex drive.

On the other hand, relaxation stimulates the “rest and restore” nervous system and the sexual appetite blooms. For a robust sex drive, you need energy, relaxation, and time.

Maybe that’s why sex is better on vacation. Not surprisingly, getting good sleep and reducing stress can get that sex drive right back where it was.

But what if your sex drive has been stable for years, but only recently has nosedived? The low libido might in fact be a symptom of an underlying medical illness and should be evaluated.

Here is a list of medical conditions that I think about when a patient tells me they are experiencing a sudden decrease in sexual desire:

Acute stress

Erectile dysfunction

Depression

Peyronie disease (penile curvature)

Sleep apnea/disorders

Diabetes mellitus

Low testosterone

Malnutrition

Hyperprolactinemia

Medications (5-alpha reductase inhibitors, opiates)

Hypothyroidism

Cancer

Anemia

Drug abuse

The ebb and flow of relationships also affects libido. The way I evaluate this is to assess whether the overall frequency of any sexual activity (i.e. ejaculation, either with a partner or with self-stimulation) has changed.

That’s because sometimes there might be a partner and sometimes not – and if there is a partner, the frequency of intercourse may not always be consistent.

If the pattern of overall sexual activity is unchanged, then desire is likely normal.

The point here is that variations in sex drive can have less to do with your attraction to someone and more to do with your own health.