You take your morning reading and it is well below your usual range. Before you worry, it helps to know that HRV is supposed to move. It responds to how you slept, what you ate and drank, how hard you trained, and what your immune system is dealing with. A low day is information, not a verdict.
Here are the most common reasons, roughly in the order we see them.
1. You slept badly, or not enough
Sleep is where most parasympathetic recovery happens. A short night, a fragmented one, or a much later bedtime than usual is the single most common cause of a next-morning dip.
What to do: nothing dramatic. Keep the day lighter if you can, and protect tonight. If short sleep has become the norm rather than the exception, that is the pattern worth addressing — we have a practical guide to building a wind-down routine that sticks.
2. You had a drink last night
Alcohol is one of the most reliable HRV suppressors there is. Even a couple of drinks in the evening commonly shows up as a lower reading and a higher resting heart rate the next morning, and larger amounts can keep it down for more than a day.
What to do: notice the pattern rather than fight the number. Many people find that seeing this effect in their own data does more than any general advice ever did.
3. You trained hard yesterday
A tough session is a deliberate stress. A dip the following morning is a normal part of adapting to it, and it usually rebounds within a day or two.
What to do: if your HRV bounces back, your recovery is keeping up with your training. If it stays suppressed for several days while you keep pushing, that is a reasonable signal to ease off.
4. Something is brewing
Your immune system responding to an infection is a real physiological load. HRV often drops — and resting heart rate often rises — before you feel properly unwell.
What to do: treat an unexplained dip alongside a raised resting heart rate as a nudge to rest, hydrate, and see how you feel tomorrow. It is not a diagnosis, and it does not replace listening to your body or talking to a doctor.
5. Stress that has not switched off
Psychological stress runs on the same nervous system as everything else. A deadline, a conflict, or a stretch of worry can keep the sympathetic side dialled up, and your morning reading will reflect it.
What to do: this is where down-regulation actually earns its keep. A few minutes of slow breathing with long exhales is one of the simplest levers — see our practical framework.
6. A late or heavy meal, dehydration, or heat
Digesting a large late dinner, being under-hydrated, or sleeping somewhere hot all ask your body to work overnight when it would rather be recovering. Each can pull a reading down on its own.
7. The reading itself was different
Before blaming your physiology, check the measurement. Readings taken standing rather than sitting, right after coffee or exercise, while talking, or with cold fingers can all come out differently. If a number surprises you, a consistent re-take is the cheapest test there is. Our guide to taking an accurate reading covers the details.
Hormonal cycles
For people who menstruate, HRV commonly runs somewhat lower in the second half of the cycle. That is a normal rhythm, not a problem, and it is one more reason your own baseline matters more than any single day.
When a dip is worth attention
One low morning is almost never meaningful. What deserves a closer look:
- A reading that stays below your usual range for several days in a row
- A dip alongside other changes — a higher resting heart rate, worse sleep, feeling run down
- A downward drift over weeks that you cannot explain
None of these mean something is wrong. They mean your recovery is not keeping pace with your load, and that is worth a conversation — with your coach, and with a doctor if you have symptoms that concern you. HRV from a phone camera is a wellness measurement, not a medical test.
How MyUltra.Coach helps
Because the app reads each check-in against your own rolling baseline, it can tell the difference between "a bit low today" and "low all week." And in a voice session, your coach can help you work out which of the reasons above is most likely — and what to change.
Get the app and start seeing what moves your number.