Check your heart rate. No gadget needed.

For most adults, 60 to 100 beats per minute at rest is normal, and people who exercise regularly often sit in the 50s. What matters more than one reading is your usual number: a rate that has drifted well above your own normal for days deserves attention, even inside the official range.

Turn one hand palm up and place two fingers of the other hand on the thumb side of the wrist, just below the crease. Press lightly until you feel the beat. Never use your thumb, which has a pulse of its own. Tapping along with each beat for 20 to 30 beats gives a reliable rate.

A rate above 100 at true rest, on several quiet checks, is worth mentioning to a doctor, especially with breathlessness, chest discomfort, faintness or fluttering. A fast rate right after activity, coffee, stress or poor sleep is usually the body doing its job. Sudden racing that starts and stops out of nowhere is its own symptom worth describing.

Often not: fit people commonly rest in the 50s, and some healthy people run slow naturally. A rate under 50 in someone who does not train, or a slow rate with dizziness, fainting or unusual tiredness, should be checked, because some medicines and some electrical problems of the heart show up exactly this way.