--- title: What time of day does your period usually start? | Niyora description: Periods most commonly start at night or early in the morning. In about one-third of cases, bleeding had already begun by the time women woke up. url: https://niyora.com/research/papers/analysis-of-the-time-of-day-of-onset-of-menstruation-1987/ --- - [Niyora](https://niyora.com/) - [Research](https://niyora.com/research/) - [Library](https://niyora.com/research/library/) - What time of day does your period usually start? Study, 1987 # What time of day does your period usually start? Periods most commonly start at night or early in the morning. In about one-third of cases, bleeding had already begun by the time women woke up. Moderate study design 86 women tracked for 4 to 6 menstrual cycles; 48 provided detailed timing information. ## What they did Researchers tracked 86 women across 4 to 6 menstrual cycles, noting the exact time menstruation began. For 48 women, they also recorded bedtime, wake time, when spotting started, and when period pain began. ## What they found 70.4% of cycles started at night or within 4 hours of waking. In 29 out of 76 cycles, bleeding was already present on waking. Premenstrual spotting lasting more than 3 hours was reported by 67% of women. Menstrual cramps occurred in about 50% of women and typically happened around the time bleeding started. Only 13% of women had their period start within the same 3-hour window across four different cycles. Almost 50% had very different starting times from cycle to cycle. ## What it means for you Menstruation commonly starts at night rather than during the day. The timing varies significantly from cycle to cycle for most women. The main limit is this is a small observational study with no comparison group. 70.4% cycles starting at night or within 4 hours of waking 67% women with spotting lasting over 3 hours 86 women in the study ## About the study Original title Analysis of the time of day of onset of menstruation Authors Donald JL, Fraser IS, Duncan L et al. Journal Clinical reproduction and fertility Year 1987 Study design Study Participants 86 Read the paper [https://pubmed.ncbi.nlm.nih.gov/3690465/](https://pubmed.ncbi.nlm.nih.gov/3690465/) ## Topics [Premenstrual syndrome (PMS)](https://niyora.com/research/topics/condition-pms/)[Dysmenorrhea and period pain](https://niyora.com/research/topics/condition-dysmenorrhea/)[Pain and headache](https://niyora.com/research/topics/symptom-pain/) Research tells you what helps on average. Niyora helps on the day it hits. Calm down, see it another way, and decide what to say, with a PMS and PMDD app built by a doctor. ## Related studies Randomised trial, 2025 Do vitamin D and E supplements reduce menstrual pain and PMS symptoms? Systematic review, 2025 Does digital healthcare help manage period pain and PMS? Cohort study, 2025 How common is PMS in Chinese teenage girls, and what factors are linked to it? Systematic review, 2025 Does teaching adolescent girls about their menstrual cycle and health help reduce period pain and PMS? Randomised trial, 2024 Does estetrol/drospirenone birth control improve PMS symptoms? Cohort study, 2024 Is there a link between sleep and menstrual problems in teenage girls? Ask AI about this page Copy prompt ChatGPT ↗ Claude ↗ Perplexity ↗ Google AI Mode ↗ Grok ↗