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Men with low sperm counts should take notice as it can be the canary in the coalmine, and sometimes it’s flagging up general poor health and a shorter lifespan. The medical terms for low sperm counts are “oligospermia” or “oligozoospermia”, and the formal diagnosis is when sperm counts fall below 15 million/ml of semen.

The term for no sperm in semen samples is “azoospermia”. Low sperm counts inevitably reduce a couple’s fertility as fewer sperm are likely to reach and fertilise an egg, but it’s still possible; plus, there are effective treatments for low sperm numbers and quality.

Men attending fertility clinics with low sperm counts are over 12x more likely to have testicles that produce low testosterone, and over half the men have osteoporosis or osteopenia (low bone density). However, low sperm counts are an indicator of several important general health conditions (and PFPs), and men with oligospermia have a significantly higher risk of these life-changing issues: [i]

  • Metabolic syndrome
  • High BMI (body mass index) and waist circumference
  • High systolic blood pressure (and risk of cardiac events or stroke)
  • Elevated LDL “bad” and low HDL “good” cholesterol (and risk of cardiac events or stroke)
  • Insulin resistance (HOMA index) (and risk of diabetes)

Causes of low sperm count

Oligospermia is sometimes temporary, making semen testing over a few months essential (it takes three months for sperm to form fully). There are a variety of causes, which are categorised into:

  1. Pre-testicular
  2. Testicular
  3. Post-testicular


Pre-testicular factors prevent the man’s testis from making healthy numbers of sperm, although the testis could be fully functioning. In these cases, low sperm production (spermatogenesis) is due to:

  • Abnormal sex hormone levels, particularly testosterone, cause “hypogonadism” (low sex hormones stop normal gonad function). For men, this is diagnosed when testosterone is under 10.5 nmol/l and/or luteinising hormone (LH) is under 9.4 IU/l.
  • Lifestyle factors include a poor diet, smoking, alcohol, environmental toxins, endocrine-disrupting chemicals (EDCs) or stress that disrupt the ability of the testicles to make sperm, which are covered in the morefertile PFPs.


 Testicular causes are due to changes within the testicles that make sperm production more difficult:

  • Undescended testis (cryptorchidism) is the incomplete descent of one or both testicles after birth and reduces fertility as the testicles overheat. This condition should have been checked for and resolved in early childhood.
  • Hydroceles involve accumulations of fluid in the spermatic cord, and this causes swollen but (usually) painless testicles and discomfort due to the heaviness of the scrotum. If there’s pain, it’s generally due to inflammation, and the swelling may be less in the morning and more later in the day.
  • Varicoceles involve impaired blood circulation due to dilation of the veins of the spermatic cord. They typically cause pain or heaviness in their scrotum, and large varicoceles involve a network of veins and have been described as a “bag of worms”.


 These are factors that cause low sperm concentration in semen; even though the testicles are making healthy numbers of sperm, few are making it outside. There are a couple of reasons this can happen:

  • Obstruction of the spermatic ducts is usually due to historical traumas or infections in the adjacent areas that have caused scarring. The obstructions constrict the tubules and prevent the passage of many sperm.
  • Infections in the tubules cause inflammation and alter the structure of the tubes, either in the prostate, epididymis, vas deferens or urethra. The infections also trigger immune responses, which cause anti-sperm antibodies in some men.

Classes of oligospermia

There are three classes of oligospermia: mild, moderate, and severe, which relate to sperm numbers in semen samples, and significant improvements can usually be made following appropriate treatment and lifestyle changes for a few months. However, it’s more likely that ICSI will be needed in severe cases.

  •  Mild oligospermia is when between 14 and 5 million sperm are in each ml of semen
  •  Moderate oligospermia samples have between 5 and 1 million sperm/ml
  •  Severe oligospermia samples have less than 1 million sperm/ml

It’s crucial to diagnose the cause of oligospermia to be able to pursue an appropriate treatment option. Once that’s done, we suggest every effort is made to focus on improving PFP health and taking specific supplements to raise your fertility.

[i] Alberto Ferlin, et al. “Sperm Count and Hypogonadism as Markers of General Male Health”, European Urology Focus, Volume 7, Issue 1, 2021, Pages 205-213, ISSN 2405-4569, https://doi.org/10.1016/j.euf.2019.08.001.
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