Why am I exhausted the week before my period?

Because the week before your period is the late luteal phase, and it is the point in the cycle where your hormones, your temperature and your sleep are all working against your energy at once. Tiredness in this window is one of the most commonly reported premenstrual symptoms, and for most women it is a normal part of the cycle rather than a sign that something is wrong.

Three things are happening at the same time.

• Progesterone rises and then falls. It peaks in the middle of the luteal phase and drops sharply in the days before bleeding starts. Progesterone has a sedating effect, so both the high and the withdrawal are felt.
• Oestrogen drops too. The fall in both hormones together is what the NHS and ACOG describe as the driver behind the cluster of premenstrual symptoms, of which tiredness is one.
• Your sleep gets worse even if your hours do not change. Core body temperature is slightly higher across the luteal phase, and reviews of sleep across the menstrual cycle find more disturbed sleep and poorer sleep quality in the days before a period. You can spend the same eight hours in bed and wake less restored.

There are two other explanations worth ruling out, because they are common and both are treatable.

• Low iron. Heavy periods are a frequent cause of iron deficiency anaemia, and tiredness is its main symptom. The clue is that the exhaustion does not lift once your period ends; it stays flat all month.
• Premenstrual dysphoric disorder (PMDD). A smaller number of women get premenstrual symptoms severe enough to disrupt work, study or relationships. That is a recognised condition with its own treatment, not something to push through.

Discharge often changes on the same schedule, becoming thicker and more noticeable as progesterone rises; see why discharge increases before your period if that's the change you're tracking alongside the tiredness. Headaches are another common companion in the same window, driven by the same hormone drop rather than the tiredness itself; see why headaches happen before your period if that's what you're noticing too. Breakouts along the jawline follow the same hormonal calendar too, driven by rising androgens rather than anything you're doing differently with your skin; see why acne flares before your period if that's part of the pattern as well. Mood swings and irritability often show up in this same window too, tracking the same hormone drop rather than the tiredness itself; see why mood swings happen before your period if that's part of what you're noticing as well. Some women also notice light spotting in this same window, a day or two before fuller bleeding starts; see why spotting can happen before your period if that's part of the pattern too. Breast tenderness is another frequent companion in the same window, driven by the same rise and fall of oestrogen and progesterone; see why breasts feel sore before your period if that's part of what you're noticing as well.

What tends to help, in the ordinary sense rather than the medical one: keeping your sleep and wake times steady across the month rather than trying to catch up at the weekend, eating regularly, and moving even when you do not feel like it. Tracking matters too, because the single most useful thing you can tell a clinician is whether the tiredness is cyclical or constant. Knowing what counts as a normal cycle length is what tells you whether this week is arriving on schedule or your cycle itself has shifted, and the best period tracker for privacy is worth reading before you trust an app with that record.

Speak to a doctor if the tiredness does not lift after your period starts, if your bleeding is heavy enough that you are changing protection every hour or two, or if your premenstrual symptoms are severe enough to interfere with daily life. The NHS advice is to see a GP when symptoms affect your day to day or when lifestyle changes have not helped.