Sperm DNA fragmentation: what the test shows, and who it's for.

A sperm DNA fragmentation test estimates what share of sperm carry broken DNA. It isn't part of a standard semen analysis, and the guidelines disagree about who needs one. NICE, whose guidance shapes NHS care in England, says not to test for it at all [1]. The American guideline says not to test routinely but to test the man when a couple has had recurrent miscarriages [2], and the European urology guideline recommends it for recurrent miscarriage, IVF that hasn't worked, or unexplained infertility [3]. High fragmentation is linked to more miscarriage across studies (about twice the risk in a 2012 meta-analysis of 16 studies) [4], but no treatment has yet been shown to turn a lower result into more live births.

What the test measures

Each sperm carries a tightly packed copy of half the father's DNA. Fragmentation means breaks in those strands. Labs report it as a DNA fragmentation index (DFI), the percentage of sperm in the sample with damaged DNA. A sperm can look normal, swim well and still carry fragmented DNA, which is the argument for testing it separately from count, motility and shape.

There are four main methods [3]. TUNEL and the comet assay measure the breaks directly; the sperm chromatin structure assay (SCSA) and the sperm chromatin dispersion test (SCD, sometimes called the Halo test) measure them indirectly. Each method and lab reports on its own scale with its own cut-offs, so ask which one was used before comparing two results. The WHO manual covers DNA fragmentation in its chapter on extended examinations rather than among the basic measures with reference limits [3].

What counts as high?

There is no agreed cut-off. The European guideline notes a suggested threshold of a DFI of 25% on SCSA, above which pregnancy rates from natural conception or IUI are lower, and says values over 50% on SCSA are linked to poorer IVF outcomes [3]. Other methods and labs use their own thresholds. If you have a result, ask which method was used and what that lab's cut-off is.

What the guidelines say

• NICE (England, 2026): "Do not carry out testing for sperm DNA integrity (fragmentation)." [1] Its reasons: the link between high fragmentation and subfertility has not been established, it is not clear which test or threshold to use, the tests are expensive and slow, and no treatment has shown a convincing benefit [10]. NICE also says not to offer supplements, antioxidants or medical treatments to improve it, and not to offer surgical sperm retrieval for it in men who have sperm in their ejaculate [11]. On the NHS in England you will not normally be offered the test.
• AUA and ASRM (US, 2020, amended 2024): not recommended in the initial evaluation of an infertile couple; for couples with recurrent pregnancy loss, the man should be evaluated with a karyotype and sperm DNA fragmentation [2].
• European Association of Urology: recommends testing couples with recurrent pregnancy loss after natural conception, couples where assisted reproduction hasn't worked, and men with unexplained infertility [3].

The guidelines are reading the same studies. Where they differ is on whether a test is worth doing when nothing proven follows from the result.

What high fragmentation is linked to

Miscarriage. A 2012 meta-analysis of 16 cohort studies and 2,969 couples found miscarriage was about twice as likely when sperm DNA damage was high (relative risk 2.16), and nearly four times as likely when measured by TUNEL (3.94) [4]. A 2019 meta-analysis compared 579 male partners of women with recurrent pregnancy loss with 434 partners of women with a live birth: the first group's fragmentation rate was on average about 12 percentage points higher [5]. Both reviews flag big differences between studies, and an association is not proof that the DNA damage caused the losses.

IVF and ICSI. A 2014 meta-analysis found high fragmentation was linked to lower pregnancy rates with IVF but not with ICSI (16 studies, 3,106 couples), and to higher miscarriage rates with both (14 studies, 2,756 couples) [6].

What is linked to higher fragmentation

• Age. The share of sperm with fragmented DNA rises with age; see the age guide [12].
• Varicocele. A varicocele is among the causes the European guideline lists, along with hormonal problems, chronic infection and smoking [3].
• Longer abstinence before a sample. A 2025 meta-analysis found abstinence of two days or less, compared with the standard 2 to 7 days, was linked to about 3.8 percentage points less fragmentation [9]. The ejaculation frequency guide covers the trade-off with count.

Can it be lowered?

Varicocele repair has the clearest evidence. A 2021 meta-analysis of 19 studies and 1,070 men with a clinical varicocele found fragmentation fell by about 7 percentage points after repair, more in men who started high [7]. Whether that leads to more live births has not been shown; see the varicocele guide.

Antioxidant supplements did not lower it in a large placebo-controlled trial. In MOXI, 174 men with male factor infertility took a combined antioxidant or a placebo; among the 44 who started with high fragmentation, it was 29.5% on the antioxidant and 28.0% on placebo at three months [8]. The supplements guide covers the rest of that evidence.

Shorter abstinence before a sample lowers it a little, as above [9]. The European guideline also mentions that a second ejaculation three hours after the first has been reported to lower it [3].

Testicular sperm for ICSI. Sperm taken directly from the testis tend to have less fragmentation than ejaculated sperm. The European guideline says using them for ICSI in men with high fragmentation should be considered experimental, offered case by case after a full discussion [3]. NICE goes further and says not to offer it for this reason, because studies comparing it with ejaculated sperm showed no benefit for pregnancy or miscarriage [10, 11].

What to do

• Start with a standard semen analysis. Fragmentation is an add-on, not a replacement, and NICE does not recommend it [1]. Our semen analysis checker puts each standard value against the WHO 2021 limit.
• If you have had two or more miscarriages, or IVF hasn't worked, ask your specialist whether a fragmentation test would change anything in your plan. Both the American and European guidelines support testing after recurrent miscarriage, and the European guideline also supports it after IVF that hasn't worked [2, 3].
• If you are offered a private test, ask which method it uses, what the lab's cut-off is, and what the clinic would do differently with a high result.
• If you have a high result, ask about a varicocele check and the timing of abstinence before the next sample before paying for supplements marketed for DNA damage.
• Keep the lifestyle basics going: smoking is linked to higher fragmentation [3], and shorter abstinence before a sample to slightly lower fragmentation [9].

Questions

Related

• Semen analysis results explained
• Varicocele and fertility
• How to improve sperm morphology
• Supplements for sperm
• When to retest

Sources

1. NICE. Fertility problems: assessment and treatment (NG257), recommendation 1.17.6. 2026.
2. American Urological Association and American Society for Reproductive Medicine. Diagnosis and treatment of infertility in men: AUA/ASRM guideline (2020, amended 2024), statements 16 and 20.
3. European Association of Urology. Guidelines on Sexual and Reproductive Health: Male Infertility, sperm DNA fragmentation section.
4. Robinson L, et al. The effect of sperm DNA fragmentation on miscarriage rates: a systematic review and meta-analysis. Human Reproduction, 2012.
5. McQueen DB, et al. Sperm DNA fragmentation and recurrent pregnancy loss: a systematic review and meta-analysis. Fertility and Sterility, 2019.
6. Zhao J, et al. Whether sperm deoxyribonucleic acid fragmentation has an effect on pregnancy and miscarriage after in vitro fertilization/intracytoplasmic sperm injection: a systematic review and meta-analysis. Fertility and Sterility, 2014.
7. Lira Neto FT, et al. Effect of varicocelectomy on sperm deoxyribonucleic acid fragmentation rates in infertile men with clinical varicocele: a systematic review and meta-analysis. Fertility and Sterility, 2021.
8. Steiner AZ, et al. The effect of antioxidants on male factor infertility: the Males, Antioxidants, and Infertility (MOXI) randomized clinical trial. Fertility and Sterility, 2020.
9. Raditya M, et al. Impact of shorter abstinence periods on semen parameters: a systematic review and meta-analysis. World Journal of Men's Health, 2025 (online 2024).
10. NICE. Fertility problems: assessment and treatment (NG257), rationale and impact, sperm DNA integrity sections. 2026.
11. NICE. Fertility problems: assessment and treatment (NG257), recommendations 1.24.6 and 1.27.1. 2026.
12. Johnson SL, et al. Consistent age-dependent declines in human semen quality: a systematic review and meta-analysis. Ageing Research Reviews, 2015.