When should I start a new cycle? (How to mark CD1)

If you’ve seen a little bit of blood, but it’s very light or intermittent, you might be wondering if that should officially start a new cycle and mark Cycle Day 1 (CD1) in your Tempdrop app?

However, Cycle Day 1 (CD1) is your first day of full, continuous bleeding—not the day you first see spotting. Spotting does NOT start a new cycle; it belongs at the very end of your previous cycle. 

Here is everything you need to know about spotting versus full flow, and why marking CD1 accurately is so important for your chart.

Spotting vs. Full Flow: What’s the Difference?

When deciding whether to mark a new cycle day, it helps to understand what your body is doing.

• Spotting:

Light brown or pink spotting several days before your actual period starts is considered premenstrual spotting. This means your body is still in its luteal phase, and you should log these days as "spotting" on your current cycle chart.

• Full Bleeding:

A true period requires the use of a pad, tampon, period underwear, or menstrual cup. The blood is typically bright or dark red and has a steady, continuous flow. The first day you experience this full flow is your official CD1.

Why Accurate CD1 Timing Matters for Your Data

It might seem like a minor detail, but accurately marking the start of a new cycle is foundational for your fertility tracking and understanding your reproductive health.

• Prevents False Cycle Truncation: Marking CD1 on your first day of light spotting prematurely closes your previous cycle on paper. For example, if you start spotting 8 days after ovulation, but don’t start a full bleed until 11 days after ovulation, you artificially cut your luteal phase in your app. This distorts your cycle history and skews future fertile window predictions.

• Uncovers Premature Progesterone Drop-Off: Premenstrual spotting is a distinct biological signal that progesterone is tapering off too early to sustain the uterine lining. By logging light bleeding as "spotting" at the end of your current cycle—rather than hitting "Start New Cycle"—you preserve crucial diagnostic data. It reveals a cycle that might look normal in total length but suffers from low functional progesterone days before your period arrives.

• Flags Upstream Root Causes: Differentiating between spotting and full flow helps you and your provider investigate underlying issues.

• Powers Productive Doctor Visits: Presenting your provider with clear distinctions between premenstrual spotting days and true full-flow days transforms vague cycle complaints into actionable medical data, helping you get targeted care faster.

Common CD1 Scenarios

What if my full period starts late in the evening?

If your period starts in the evening, most users mark that day as Cycle Day 1, as long as bleeding begins before they go to bed or before midnight.

The most important thing is to choose a rule that works for you and apply it consistently every cycle. For example, if you decide that any bleeding before 8pm counts as the same day, use that same cut-off each time.

If bleeding starts later in the day, you can also use the Notes feature to record the time it began.

What if I have 3 or 4 days of spotting before the heavy bleeding starts?

Do not start a new cycle yet! Keep marking those days as spotting at the end of your current cycle. Only hit "Start New Cycle" on the day the true, full flow arrives.

What if my period arrives, but I didn’t see a temperature shift?

If you do not see a temperature shift, this typically indicates that ovulation didn't occur. The bleeding is therefore considered breakthrough bleeding rather than a true period, which follows ovulation.

Tempdrop recommends marking this as non-menstrual bleeding and continuing to log data on your current chart.

If you are following a fertility awareness method, follow your method’s specific rules for how to handle breakthrough bleeding.

What if I enter my cycle day 1 on the wrong day?

You can remove cycle day 1 in the app. Go to the date that is incorrectly marked. Click menstruation on the symptoms screen, then untoggle ‘cycle day 1. This will prompt a message saying your cycle will be deleted. Please note: this does not delete any symptom data you have entered, including bleeding; it only removes the cycle start date. 

You can then enter the correct cycle day 1.