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Condition

Necrozoospermia (Low Sperm Vitality)

Necrozoospermia is a semen abnormality in which an unusually high proportion of sperm are non-viable, meaning they are not alive at the time of testing. It is diagnosed with sperm vitality testing and must be distinguished from asthenozoospermia, where sperm may be alive but have poor or absent movement.

Also known as: Low sperm vitality, Poor sperm vitality, Dead sperm in semen, High percentage of dead sperm, Necrospermia, Necrozoospermia, Low viable sperm, Low sperm viability, Non-viable sperm, Dead sperm count

Symptoms8 listed
ICD-10N46.9
TreatableYes
DE
Medically reviewed by Dr. Elif Yılmaz, MD, FECSM
Last reviewed 23 August 2026
✓ Clinician reviewed
Necrozoospermia✓ Clinician-reviewed information
Key takeaways
  • Necrozoospermia means a high proportion of sperm in the ejaculate are non-viable.
  • It is different from asthenozoospermia because immotile sperm are not necessarily dead.
  • Sperm vitality testing is especially important when many or all sperm appear immotile.
  • Causes may include infection, inflammation, oxidative stress, prolonged abstinence, heat exposure, testicular dysfunction, and other reproductive conditions.
  • Treatment depends on the cause, while IVF/ICSI may be considered when adequate viable sperm cannot be obtained for natural conception or simpler fertility treatments.

Overview

Necrozoospermia is a semen-analysis abnormality in which a lower-than-expected proportion of sperm are alive.

Sperm vitality measures whether sperm cells are viable, regardless of whether they are moving.

This distinction is important because a sperm can be:

  • Alive and moving

  • Alive but immotile

  • Dead and immotile

A routine semen analysis can identify movement, but additional vitality testing may be required to determine whether immotile sperm are still alive.

Necrozoospermia vs asthenozoospermia

These conditions are often confused.

Asthenozoospermia means sperm motility is reduced.

Necrozoospermia means sperm vitality is reduced.

A man can therefore have very poor sperm motility while many sperm remain viable.

Conversely, if a high proportion of sperm are dead, both motility and vitality will be low.

This difference is particularly important when considering assisted reproduction because viable but immotile sperm may still potentially be used for ICSI.

Why sperm vitality matters

For fertilization, sperm must be biologically viable.

If a high proportion of sperm are non-viable, the effective number of sperm capable of fertilization is reduced.

Severe necrozoospermia can therefore substantially impair fertility.

However, fertility assessment should not rely on vitality alone.

The full semen analysis, female-partner factors, fertility history, and underlying cause all matter.

Types of necrozoospermia (low sperm vitality)

Partial Necrozoospermia
A substantial proportion of sperm are non-viable, but some living sperm remain in the ejaculate. These viable sperm may sometimes be sufficient for natural conception, IUI, IVF, or ICSI depending on the overall fertility situation.
Severe Necrozoospermia
Only a small proportion of sperm are viable. This can significantly reduce fertility potential and may require more advanced assisted reproductive strategies.
Complete Necrozoospermia
No viable sperm are identified in the semen sample. This diagnosis requires careful confirmation because laboratory handling and testing technique can influence results. In selected cases, viable sperm may still be found through testicular sperm retrieval.
Transient Necrozoospermia
Sperm vitality temporarily falls because of a reversible factor such as: Fever Infection Inflammation Prolonged abstinence Heat exposure Acute systemic illness Repeat semen testing may show improvement after the underlying factor resolves.
How common is it?
Necrozoospermia is considered an uncommon semen abnormality, and exact prevalence in the general male population is not well established. Studies of infertile men suggest that severe or complete necrozoospermia is rare compared with abnormalities of sperm count, motility, or morphology.
Source: who.int

Symptoms

Difficulty conceiving
Low sperm vitality on semen analysis
High percentage of non-viable sperm
Very low sperm motility
Complete sperm immotility
Repeated abnormal semen analyses
Genital infection or inflammation in some men
Other male infertility abnormalities

Causes

Genital tract infection
Inflammation
Oxidative stress
Prolonged abstinence
Testicular dysfunction
Varicocele
Recent high fever
Severe systemic illness
Excessive testicular heat exposure
Smoking
Environmental toxins
Occupational toxin exposure
Certain medications
Chemotherapy Radiotherapy
Testicular injury
Hormonal abnormalities in selected patients
Improper semen sample collection or handling
Delayed laboratory analysis
Idiopathic causes where no clear explanation is found

Risk factors

Previous or current genital infection
Varicocele
Smoking
Excessive heat exposure
Prolonged abstinence
Recent febrile illness
Testicular disease
Chemotherapy
Radiotherapy
Occupational toxins
Metabolic disease
Other severe semen abnormalities
Poor sample handling or delayed testing

How it is diagnosed

Diagnosis requires sperm vitality testing.

Semen analysis

Routine semen analysis measures:

  • Semen volume

  • Sperm concentration

  • Total sperm number

  • Motility

  • Morphology

If a large proportion of sperm are immotile, the laboratory should assess vitality.

Sperm vitality testing

Vitality testing determines whether immotile sperm are alive or dead.

Methods may include:

  • Eosin-nigrosin staining

  • Hypo-osmotic swelling testing

  • Other validated laboratory techniques

The WHO semen manual recommends vitality assessment particularly when sperm motility is markedly reduced.

Why vitality testing matters

If sperm are immotile but alive, the diagnosis is more consistent with severe asthenozoospermia.

If they are immotile and non-viable, necrozoospermia is present.

This distinction can directly affect fertility treatment planning.

Repeat semen analysis

Abnormal vitality should generally be confirmed because temporary factors can alter semen quality.

The clinician may consider:

  • Recent fever

  • Infection

  • Abstinence duration

  • Sample transport

  • Delay before laboratory analysis

  • Medications

  • Heat exposure

  • Lifestyle factors

Medical evaluation

Persistent necrozoospermia may prompt assessment of:

  • Fertility history

  • Genital infections

  • Varicocele

  • Testicular disease

  • Medications

  • Smoking

  • Heat exposure

  • Occupational toxins

  • Previous chemotherapy or radiotherapy

  • Chronic disease

Additional testing

Depending on findings, investigations may include:

  • Urinalysis

  • Urine culture

  • STI testing

  • Hormonal testing

  • Scrotal examination or ultrasound

  • Additional male infertility testing

When to see a doctor
  • A semen analysis reports low sperm vitality.
  • Most or all sperm appear immotile.
  • Repeat semen tests show persistent low viability.
  • You and your partner have difficulty conceiving.
  • The laboratory reports complete necrozoospermia.
  • You have symptoms of genital infection or inflammation.
  • You have a varicocele and abnormal semen parameters.
  • You recently had chemotherapy or radiotherapy.
  • You want to understand whether viable sperm can still be used for IVF/ICSI.
  • Previous fertility treatment failed because no viable sperm could be identified.
Reducing your risk
  • Stop smoking.
  • Avoid excessive testicular heat.
  • Avoid very prolonged abstinence when trying to conceive.
  • Seek treatment for genital infections.
  • Maintain a healthy body weight.
  • Manage diabetes and metabolic disease.
  • Avoid anabolic steroid misuse.
  • Avoid unnecessary testosterone use when fertility is desired.
  • Use workplace protection around reproductive toxins.
  • Discuss fertility preservation before chemotherapy or radiotherapy.
  • Follow proper semen collection and transport instructions for laboratory testing.

Common questions

What is necrozoospermia?
Necrozoospermia means that an unusually high proportion of sperm in the semen are non-viable or dead.
Is necrozoospermia the same as low sperm motility?
No. Low sperm motility means sperm do not move well. Some immotile sperm are still alive. Necrozoospermia specifically refers to reduced sperm vitality.
How do you know whether immotile sperm are alive?
A laboratory can perform sperm vitality testing, such as eosin-nigrosin staining or hypo-osmotic swelling testing.
Can dead sperm fertilize an egg?
Non-viable sperm cannot normally fertilize an egg. Fertility treatment therefore focuses on identifying viable sperm.
Can necrozoospermia cause infertility?
Yes. Severe reduction in viable sperm can substantially reduce fertility potential.
Can necrozoospermia improve?
Sometimes. If the cause is temporary, such as fever, infection, inflammation, or prolonged abstinence, semen vitality may improve after the underlying factor is corrected.
Can infection cause dead sperm?
Genital tract infection or inflammation can be associated with oxidative stress and poorer semen quality, including reduced sperm vitality in some men.
Can prolonged abstinence lower sperm vitality?
Very prolonged abstinence can increase the proportion of older sperm within the ejaculate and may negatively affect some semen-quality parameters.
Can varicocele cause necrozoospermia?
Varicocele can be associated with oxidative stress and impaired semen quality and may contribute in some men, although it is not the only possible cause.
What does 0% sperm vitality mean?
It means no viable sperm were identified in the tested sample. The result should usually be carefully confirmed because laboratory technique, sample handling, and transient factors can affect findings.
Can ICSI be used with necrozoospermia?
Yes, if viable sperm can be identified. Embryologists may use specialized techniques to identify living sperm for ICSI.
What if all sperm in the semen are dead?
In selected men with complete necrozoospermia, viable sperm may sometimes be retrieved directly from the testis for use with ICSI.
Why can testicular sperm be alive when ejaculated sperm are dead?
In some cases, sperm may become damaged during storage or transit through the reproductive tract. Testicular retrieval can bypass this pathway and may provide viable sperm in selected patients.
Is testicular sperm extraction always necessary?
No. It is generally considered only when adequate viable sperm cannot be identified in the ejaculate or when the reproductive team believes testicular retrieval offers a meaningful advantage.
Can supplements treat necrozoospermia?
Antioxidants are sometimes used in male infertility, but evidence for improving pregnancy and live-birth outcomes is inconsistent. Treatment should focus first on identifying reversible causes.
Which doctor treats necrozoospermia?
An andrologist or reproductive urologist can evaluate persistent low sperm vitality and coordinate treatment with an embryology or assisted-reproduction team.

Sources

  1. WHO Laboratory Manual for the Examination and Processing of Human Semen, Sixth Edition https://www.who.int/publications/i/item/9789240030787
  2. EAU Guidelines on Sexual and Reproductive Health — Male Infertility https://uroweb.org/guidelines/sexual-and-reproductive-health/chapter/male-infertility
  3. Diagnosis and Treatment of Infertility in Men: AUA/ASRM Guideline https://www.auanet.org/guidelines-and-quality/guidelines/male-infertility