Peak and Trough
Peak and trough are the highest and lowest hormone levels between two doses. The peak comes a while after a dose goes in; the trough is just before the next one. The gap between them depends on the medicine and how it is taken.
Where you'll meet it
When a prescriber asks when you last took your dose before a blood test, and in forum threads about injection schedules and why levels "crash" before the next shot.
Why it matters for blood tests
A level only means something if you know where in the cycle it was taken. The same person can look very high a day or two after an injection and low the day before the next one, with nothing wrong. Many prescribers ask for trough levels, taken just before a dose, because they are the easiest to compare over time. Others want a mid-cycle figure. Ask which your prescriber wants and keep the timing the same each time.
Which forms swing most
Injections have the widest swings, and the longer the gap between doses, the wider they get. Patches, gels and daily tablets give steadier levels. Long-acting testosterone undecanoate sits in between. Some people notice the trough as tiredness, low mood or, on testosterone, spotting; that is worth telling your prescriber, because a change of interval or form can smooth it out. How to read your hormone blood results goes further.
Related pages
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The Start Here guide covers what hormones change, how people get a prescription, what the blood tests are for and what it costs.
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