Is This Normal Now

Resting Heart Rate 120 When Sick

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Resting Heart Rate of 120 While Sick: What It Can Mean

Disclaimer: This article is for general information only and is not medical advice or a diagnosis. If you have severe symptoms or think it may be an emergency, call your local emergency number.

You are sick, trying to rest, you check your smartwatch, and it says your resting heart rate is 120.

Are you dying? Is this just the fever? Is your watch broken? Should you go to the ER or just close your eyes and pretend you did not see it?

This article walks through what a resting heart rate of 120 while sick can mean, when it is urgent, and what you can actually do about it.

First: What Is a Normal Resting Heart Rate?

In most healthy adults, a normal resting heart rate (RHR) is usually around 60–100 beats per minute (bpm), according to major cardiology guidelines such as the American Heart Association. Athletes or very fit people can even sit in the 40s–50s.

Where does 120 bpm fit in?

  • Over 100 bpm at rest is called tachycardia (a faster-than-normal heart rate).
  • 120 bpm at rest is clearly elevated and not in the normal range for most adults.

Quick takeaway: 120 at rest is definitely high, but context matters a lot.

Why Does Your Heart Rate Go Up When You Are Sick?

Many illnesses make your heart beat faster, even when you are just lying in bed. There are several common reasons.

1. Fever Revs Up Your Heart

For many people, heart rate increases as body temperature goes up. A rough rule doctors sometimes use is:

For every 1°C (about 1.8°F) increase in body temperature, heart rate can go up by roughly 10–15 bpm.

If you normally sit at 70 bpm and have a decent fever, you might see numbers in the 90s or low 100s. Higher fevers or more severe infections can push it further.

Example:

  • Normal: 70 bpm
  • You get the flu with a 102°F fever, and your resting heart rate could jump to 100–110 bpm.

Takeaway: Fever alone can push your heart rate up, but 120 at rest is still on the higher side and deserves attention, especially if you feel unwell in other ways.

2. Dehydration

When you are sick, you might sweat from fever, vomit, have diarrhea, or not feel like drinking anything. Less fluid in your body means lower blood volume. To keep blood and oxygen moving, your heart may beat faster.

Signs dehydration may be part of the problem include:

  • Dark yellow urine or not peeing much
  • Dry mouth or cracked lips
  • Feeling weak, dizzy, or lightheaded when standing

Takeaway: If you are sick and not drinking much, a high resting heart rate can be your body’s red flag for needing fluids.

3. Stress, Anxiety, and Pain

Being sick is stressful. If you are anxious, in pain, or panicking because you saw 120 on your smartwatch, your body pumps out stress hormones such as adrenaline, which speed up the heart.

You may notice:

  • Heart racing when you are worrying or searching symptoms online
  • Chest tightness or a pit in your stomach
  • Shaky hands or feeling wired

Takeaway: Stress can stack on top of illness and fever, pushing your heart rate even higher.

4. Medications That Raise Heart Rate

Some illness-related medications can increase heart rate, for example:

  • Decongestants such as pseudoephedrine or phenylephrine in some cold and flu tablets
  • Some inhalers for asthma or bronchitis (short-acting bronchodilators)
  • High caffeine intake, such as energy drinks or strong coffee, on top of being sick

If you started a new medication around the time your heart rate jumped, it is worth checking the label and calling a healthcare provider or pharmacist.

Takeaway: A combination of cold medicine, caffeine, and fever can significantly boost heart rate.

5. The Infection Itself

Some infections can directly stress the heart, especially more serious ones.

Your body may increase heart rate to:

  • Fight infection
  • Deliver more oxygen to tissues
  • Compensate for lower blood pressure

Sometimes, a very high heart rate at rest is one of the clues of a more serious infection or sepsis, especially when combined with other red-flag symptoms.

Takeaway: A fast heart rate can be your body’s alarm system, not just a random glitch.

When Is a Resting Heart Rate of 120 While Sick Less Concerning, and When Is It Not?

There is no single magic number that is safe or unsafe for everyone, but patterns and red flags matter.

Situations Where It May Be Less Alarming (But Still Worth Watching)

It may be less concerning if:

  • You have a known fever (such as 101–103°F) and feel like you have a typical viral illness such as the flu or COVID-19.
  • You just checked after walking to the bathroom, climbing stairs, or changing positions.
  • You are anxious, in noticeable pain, or just took a decongestant or inhaler.
  • The number comes down to more reasonable territory (for example, below 100 bpm) within 10–20 minutes of resting and hydrating.
  • You otherwise feel moderately sick but not severely unwell: no trouble breathing, no chest pain, not confused, and can drink fluids.

Even in these cases, 120 is high enough that you should keep a close eye on it, address fluids, fever, and rest, and call your doctor or a nurse line if it keeps happening.

Takeaway: Less concerning does not mean ignore it. It means watch it closely and correct what you can.

Red Flags: When a Resting Heart Rate of 120 While Sick Is an Urgent Problem

Call a doctor, urgent care, or go to the emergency room or call emergency services if you have a high heart rate around 120 or more at rest plus any of these:

  • Chest pain, pressure, or tightness, especially if it spreads to the arm, jaw, or back
  • Trouble breathing or feeling like you cannot get enough air
  • Feeling faint, passing out, or almost passing out
  • New confusion, trouble thinking clearly, or not acting like your normal self
  • Cold, clammy, or pale, gray, or blue skin, lips, or nails
  • Very low blood pressure readings, or feeling extremely weak and woozy
  • Fast heart rate that stays at or above 120 at rest for an hour or more, even after lying down, drinking fluids if you are allowed to, and treating fever with medications like acetaminophen or ibuprofen if they are safe for you
  • History of heart or lung disease, such as heart failure, coronary artery disease, prior heart attack, arrhythmia, COPD, severe asthma, or pulmonary embolism, and now your heart is much faster than usual
  • You have COVID-19, flu, or another infection and are feeling unusually weak or like something is very wrong.

If you are pregnant, elderly, or have major health conditions, do not wait as long to be checked.

Takeaway: High heart rate plus shortness of breath, chest pain, confusion, or collapse means you should seek help urgently.

How to Check if It Is Really Your Resting Heart Rate

Before reacting to a number, make sure you are checking it correctly.

To get a more accurate resting heart rate:

  1. Sit or lie down for at least 5–10 minutes in a quiet, calm environment.
  2. Avoid talking, scrolling through stressful content, or watching intense television.
  3. Use one method:
    • A smartwatch or fitness tracker, understanding they are not perfect, or
    • A manual pulse check by placing two fingers on your wrist on the thumb side or on your neck, counting beats for 30 seconds and multiplying by 2.
  4. Repeat it 2–3 times, a few minutes apart.

If every time you check you are between about 110–130 bpm while truly resting, that is meaningful information.

Takeaway: If your watch says 120 right after you walked up stairs, that is not your resting heart rate.

What You Can Do at Home

If you do not have red-flag symptoms and you are not in a medical emergency, there are practical steps you can take at home.

1. Hydrate

  • Sip water, oral rehydration solutions, or broths regularly.
  • If you have had vomiting or diarrhea, electrolytes such as oral rehydration solutions or electrolyte drinks can help.
  • Aim for steady sipping, not large amounts at once if your stomach is sensitive.

Watch for improvement over 30–60 minutes. If your heart rate eases down as you hydrate and rest, that is reassuring but still worth mentioning to your doctor.

2. Treat Your Fever if It Is Safe for You

Ask your doctor what is safe based on your conditions, but many adults use:

  • Acetaminophen (Tylenol)
  • Ibuprofen (Advil, Motrin), which is not safe for everyone, such as some people with kidney, gastrointestinal, or heart conditions

Treating fever can lower body temperature, reduce discomfort and pain, and often help bring the heart rate closer to baseline. Recheck your heart rate 30–60 minutes after fever medicine.

3. Rest Fully

  • Lie down or sit reclined.
  • Limit screen time and stimulation.
  • Skip heavy meals, intense activity, or long hot showers.

If moving from lying to standing sharply increases your heart rate and makes you dizzy, sit or lie back down and call your doctor.

4. Check Your Medications and Stimulants

  • Review any cold or flu medications, inhalers, or decongestants you have started.
  • Avoid extra caffeine from coffee, tea, soda, or energy drinks.
  • Avoid nicotine and recreational drugs.

If you suspect a specific medication is raising your heart rate, call your doctor or pharmacist before stopping any prescription on your own.

5. Calm Your Nervous System

Your body does not separate the stress of infection from the stress of seeing a high heart rate.

Consider:

  • Slow breathing, such as inhaling for 4 seconds and exhaling for 6–8 seconds, repeated for a few minutes.
  • Progressive relaxation, gently tensing then relaxing muscle groups from toes to head.
  • Listening to something soothing instead of reading alarming stories.

If your heart rate drops a bit when you calm your body and mind, that is useful information.

Takeaway: You cannot always fix the illness instantly, but you can reduce how activated your system is.

When to Call a Doctor About a Resting Heart Rate of 120 While Sick

If you are unsure, calling is reasonable. In general, reach out to a healthcare provider the same day if:

  • Your resting heart rate is consistently at or above about 110–120 bpm while sick, even when lying still.
  • It is noticeably higher than your normal baseline, such as usually 60 and now 120.
  • You have had symptoms for more than a day or two and they are not improving.
  • You have other conditions such as heart disease, lung disease, diabetes, kidney disease, or are pregnant.
  • You are not sure if your symptoms mean urgent or emergency care.

Things to have ready when you call include:

  • Your heart rate range, for example 110–130 at rest for 24 hours.
  • Temperature readings and how high your fever is.
  • Any medications you are taking.
  • Other symptoms such as shortness of breath, chest discomfort, dizziness, confusion, or color changes.

Takeaway: If you are asking whether it is bad enough to call, that is already a good sign you should call.

Special Situations

1. You Have Known Heart Problems

If you have a history of:

  • Arrhythmias such as atrial fibrillation or supraventricular tachycardia (SVT)
  • Prior heart attack or heart failure
  • A known structural heart condition or are on heart medications such as beta-blockers

and now your resting heart rate is 120 while you are sick, call your cardiologist or primary care provider promptly, or follow any “when to call” plan they gave you.

2. You Recently Had COVID-19, Flu, or Another Major Infection

Some people notice their resting heart rate stays high for days or weeks after the main infection symptoms improve. This can sometimes be part of post-viral syndromes or conditions affecting how the nervous system regulates heart rate.

If your resting heart rate stays elevated for more than a couple of weeks, or is interfering with your ability to function, get evaluated. Your provider may check lab work, an ECG, or other tests to rule out lingering issues such as anemia, thyroid problems, persistent inflammation, or heart involvement.

Takeaway: Being past the worst of the virus but still having a racing heart is a valid reason to be seen.

Bottom Line: Is a Resting Heart Rate of 120 While Sick Dangerous?

Sometimes it is your body’s normal reaction to fever, dehydration, and stress. Sometimes it is an early warning sign of something more serious, such as a severe infection, heart strain, or another underlying problem.

So:

  • Do not ignore 120 bpm at rest.
  • First, address what you can at home: fluids, fever control, rest, review medications, and calm your system.
  • Pay close attention to how you feel overall, not just the number.
  • If the rate stays high, you feel worse, or you see any red-flag symptoms, seek urgent or emergency care.

Listening to your body and acting on concerning signs is appropriate and important.

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