Why do I keep getting sick? What's normal, what's behind it, and when to look further

Short answer

Why do I keep getting sick? Usually because of exposure, short sleep or a heavy stress stretch, not a broken immune system. If you catch two or three colds a year and each clears within about 10 days, you are at the adult average. If you get two or more sinus infections a year, yearly pneumonia, or infections that are hard to clear, ask a doctor to look further.

If you have started to think of yourself as "the one who always gets sick", or wondered whether you are just weak, that is not a character flaw and it is not your fault. Catching colds is mostly about which viruses reach you and what state your body is in when they do. Before you blame yourself, check what your body already recorded: the short nights, the stressful weeks, the people coughing around you.

Note: this article explains why healthy adults catch frequent infections and is not medical advice. It cannot tell you why you in particular keep getting sick. Infections that are severe, unusual, slow to clear or keep returning need a clinician.

When it's not just bad luck

Most frequent colds are a nuisance rather than a sign of hidden illness. A smaller group of patterns deserves a doctor's attention, and it is worth knowing them first.

See a doctor for the illness itself if you have any of the signs the CDC lists as reasons to seek care for a cold: trouble breathing or fast breathing, dehydration, a fever that lasts longer than 4 days, symptoms that last more than 10 days without getting better, symptoms such as fever or cough that improve and then return or worsen, or a chronic medical condition that gets worse (CDC). If breathing trouble is severe, call 911.

See a doctor about the pattern if infections are not just frequent but unusual. The Jeffrey Modell Foundation, working with immunology experts, publishes 10 warning signs of primary immunodeficiency in adults — conditions in which part of the immune system does not work as it should (Jeffrey Modell Foundation). They include:

• two or more new ear infections within 1 year;

• two or more new sinus infections within 1 year, in the absence of allergy;

• one pneumonia per year for more than 1 year;

• chronic diarrhoea with weight loss;

• recurrent viral infections such as colds, herpes or warts;

• a recurrent need for intravenous antibiotics to clear infections;

• recurrent deep abscesses, persistent thrush or fungal infections, or a family history of immunodeficiency.

The foundation's advice is to speak to a physician if two or more of the signs apply. It estimates that about 1 in 500 people has one of the known primary immunodeficiencies. That makes these conditions uncommon, but not so rare that a doctor should wave the question away when the pattern fits.

Notice what is on the list and what is not. Ordinary colds that come and go are only one item among ten. What usually stands out in immune problems is infections that are deeper, more serious, harder to clear or caused by unusual germs — not simply a lot of runny noses.

How often is it normal to get sick?

Every year in the United States, adults have an average of two to three colds, and children often have more, according to the CDC (CDC). Colds usually last less than a week. So if you count three colds since last autumn, you are not an outlier. You are close to the middle.

Averages hide a wide spread, though. Some adults go a whole year without a cold; others live with toddlers or teach a classroom and catch far more. Here is how to read the most common versions of the question.

Why do I keep getting sick every month?

Getting sick every month is four to six times the adult average of two to three colds a year, so it is worth a closer look, but it is not automatically a sign of disease. Start with what is around you: a young child at home, a classroom, a hospital ward or an open-plan office can supply a new virus almost every week. In a Utah study that swabbed families weekly for a year, a respiratory virus was found in 26% of all person-weeks, and people living with children had about 3 more weeks of virus detection over the year than people living alone (doi.org). If the monthly illnesses are colds that clear within a week and you feel well between them, exposure, sleep and stress are the usual suspects. If they are sinus, ear or chest infections, or you never fully feel well in between, see a doctor.

Why do I keep getting sick back to back?

Getting sick back to back usually has one of two explanations: a second, different virus arriving before you have fully recovered from the first, or one illness that never quite cleared. Different respiratory viruses circulate at the same time, so a cold followed by another cold a week later is common in a busy household. In the Utah family study, viruses stayed detectable for 2 weeks or less on average, but 16% of episodes lasted 3 weeks or longer (doi.org). The pattern to take seriously is the one the CDC names: symptoms that improve and then return or get worse, or that last more than 10 days without getting better (CDC). That can mean a complication such as a bacterial sinus or chest infection.

Why am I getting sick so often all of a sudden?

When you suddenly start getting sick more often, ask what changed in the last few months. Common answers are a new job or commute, a child starting daycare or school, a run of short nights, a new caring role, or a stressful stretch that has not let up. Each of these has evidence behind it, covered below. Less often, a sudden change reflects something medical, such as a new medicine that affects the immune system, diabetes, low iron, a thyroid problem or a lingering post-viral illness. A practical approach is to write down when the change started and what else happened around then, and to ask your doctor whether any blood tests make sense. If you were diagnosed with COVID-19 and have felt unwell since, read about long COVID symptoms.

Why do I get sick every winter?

Getting sick every winter is expected rather than a sign that something is wrong with you. The CDC notes that you can catch a cold any time of year, but that many respiratory viruses, including influenza and RSV, usually circulate during winter, while other cold-causing viruses circulate in spring, summer or autumn (CDC). Winter also brings more time indoors with other people and, for many, shorter and more disrupted nights over the holidays. A winter cluster of two or three colds fits the adult average. A winter of repeated chest infections or pneumonia does not, and is worth raising with a doctor.

Why do I keep getting sick since my kid started daycare or school?

This is one of the most common and most predictable reasons adults get sick more often. Young children catch many viruses, bring them home and share them generously. In the Utah study, children under 5 had nearly four times the odds of older family members of having a virus detected in a given week, and people living with children had a virus detected for about 3 extra weeks over the year compared with people living alone (doi.org). The first year or two of daycare is often the hardest for the whole household. It says nothing about the strength of your immune system. Handwashing, rest when you can get it and not running yourself into the ground are the realistic levers.

Why do I keep getting sick? The usual causes, in the order to check

Whether a virus that reaches you turns into a cold depends on two things: how often you are exposed, and how ready your body is when it happens. The strongest research on the second part comes from "viral challenge" studies, where healthy volunteers are given cold virus in nose drops, kept in quarantine and watched to see who gets ill. These studies are useful because everyone gets the same dose of the same virus, so differences in who falls ill point to differences in the people.

Does lack of sleep weaken your immune system?

Yes — in the most careful studies, people who slept less before meeting a cold virus were more likely to get sick. In a 2015 study, 164 healthy adults aged 18 to 55 wore a wrist sleep tracker for 7 days before being given rhinovirus. Those who slept less than 5 hours a night had 4.50 times the odds of developing a cold compared with those who slept more than 7 hours, and those who slept 5 to 6 hours had 4.24 times the odds (doi.org). Odds ratios are not the same as "times as likely", and the confidence intervals were wide, so the exact multiple is uncertain; the direction is clear: short sleepers were more likely to get ill. People sleeping between 6 and 7 hours had no clearly higher risk. The link held after the researchers accounted for prior antibody levels, demographics, season, body mass index, psychological factors and health habits.

An earlier study by the same group, with 153 adults who kept 14-day sleep diaries, found a similar pattern: people sleeping less than 7 hours had 2.94 times the odds of developing a cold compared with those sleeping 8 hours or more (doi.org). In that study, sleep efficiency — the share of time in bed actually spent asleep — was also linked to colds: people with less than 92% efficiency had 5.50 times the odds of getting sick compared with those at 98% or above.

The two studies disagree on one detail, and it is worth being clear about it. In the 2015 study, where sleep was measured by a device rather than by people's own reports, broken sleep was not linked to colds; only short sleep was. So the firmest message is about total sleep: a run of nights under 6 hours is the pattern most clearly tied to catching a cold. Interestingly, in the 2009 study, how rested people felt was not associated with colds — so you cannot rely on how you feel to judge whether your sleep is protecting you.

If you have been running on short nights for a while, our guide to sleep debt and whether you can catch up explains what recovery sleep can and cannot repair.

Can stress make you get sick more often?

Yes. In a classic study published in 1991, 394 healthy adults filled in questionnaires about psychological stress and were then given one of five common cold viruses. As stress scores rose, infection rates climbed from about 74% to about 90%, and clinical colds from about 27% to about 47% (doi.org). The relationship was dose-dependent — more stress, more risk — and it looked similar across all five viruses.

Two details make this study more convincing than most. The researchers ruled out the obvious explanations: smoking, alcohol, exercise, diet, sleep quality, white-cell counts and total antibody levels did not explain the link. And the extra risk came from more people becoming infected, not from stressed people simply reporting more symptoms. Stress, in other words, did not just make colds feel worse. It made the virus more likely to take hold.

This matters for the way people talk to themselves. A stressful quarter is not a test of willpower that you failed if you then catch a cold. It is a physical load, and the body responds to it whether or not you feel you are "coping".

Who you spend your days with

Exposure is often the whole answer, and it is the one people overlook because it feels too simple. Living with young children, working in schools, healthcare, retail or crowded offices, commuting on packed transport and caring for a sick relative all raise the number of viruses that reach you. The Utah family study found that 56% of virus detections came with symptoms and the rest were silent (doi.org), which means people around you can carry a virus without looking ill.

You cannot opt out of your life, but you can see it clearly. If you work in a classroom and have two preschoolers at home, four or five colds a year is a reasonable consequence of your circumstances, not a symptom.

Vitamin D, exercise, smoking and alcohol

Vitamin D. A 2017 meta-analysis of 25 randomised trials with 11,321 participants found that vitamin D supplements slightly reduced the risk of acute respiratory infections overall (adjusted odds ratio 0.88) (doi.org). The benefit was much larger in people who started out very deficient — below 25 nmol/L — and in trials using daily or weekly doses rather than occasional large ones. So if your level is low, correcting it may help; if it is above that level, the effect was smaller. Ask your doctor whether a vitamin D test makes sense for you rather than choosing a dose yourself.

Exercise. In a 12-week study of 1,002 adults aged 18 to 85 during autumn and winter, people who did aerobic exercise on 5 or more days a week had 43% fewer days with upper respiratory infections than people who were active on 1 day a week or less (doi.org). This was an observational study, so fitter people may differ in other ways too, but the direction is reassuring: regular movement goes with fewer sick days, not more.

Smoking and alcohol. If you smoke or vape, or drink most evenings, that is worth discussing with your doctor as part of the picture. One indirect route is clear from the sleep research above: anything that cuts your nights short adds to the risk. We have written about how alcohol affects the next night's sleep and heart rate.

Medical reasons to rule out

When exposure, sleep and stress do not explain the pattern, a doctor may consider medical causes, depending on your history. Examples include diabetes, low iron, an underactive thyroid, medicines that dampen the immune system, allergies that are being mistaken for colds, and post-viral conditions such as long COVID. Some of these are easy to test for. If tiredness, feeling cold and weight changes come along with the infections, our guide to whether it's your thyroid or something else may help you frame the question.

Allergies deserve a special mention. A constantly runny nose, sneezing and an itchy throat every spring can feel like "always being sick" when there is no infection at all. The immunodeficiency warning signs themselves count sinus infections only "in the absence of allergy", a reminder that the two can be confused.

Why do I get sick on vacation?

Getting sick on the first days of a vacation, or every weekend, has a name: leisure sickness. Dutch researchers described it in 2002 as developing symptoms of sickness during weekends or vacations (doi.org). In a representative sample of 1,128 men and 765 women, 3.6% of men recognised themselves in the description of weekend sickness and 3.2% in vacation sickness; for women, the figures were 2.7% and 3.2%.

The most common complaints were headache or migraine, fatigue, muscle pain and nausea, and colds and flu-like illness were often reported in relation to vacations. People with the pattern had usually had it for over 10 years, and it tended to start during a stressful period. What set them apart from people without it was not what they did on their days off — lifestyle and leisure activities did not differ — but heavy workload, a strong sense of responsibility for work and difficulty switching off.

What leisure sickness is not, yet, is explained. The study was a pilot, and its authors called for future research to test what actually causes the pattern. One idea is that the drop in pressure after a long push is the moment the body finally "lets go"; another is that people who never stop simply notice symptoms once they slow down. Neither has been proven. Travel adds its own ingredients: airports and planes full of people, disrupted sleep, time-zone changes and late nights.

What you can do with that: if you keep crashing on day two of every holiday, the vacation is probably not the problem — the weeks before it are. A practical approach is to taper rather than sprint into a holiday: protect your sleep in the final week, avoid the all-nighter to clear your inbox, and plan a gentler first day. Our article on stress and weekend recovery looks at why switching off can be harder than it sounds.

What helps — and what doesn't

There is no shortcut that makes an immune system "stronger" overnight, and much of what is sold as an immune booster has little evidence behind it. What the research above does support is a short list.

• Protect total sleep first. The clearest signal in the viral-challenge studies is about short nights: under 6 hours was where risk rose most. Aim for a steady bedtime rather than heroic catch-up weekends.

• Lower the stress load where you can. Not by trying harder to be calm, but by removing one recurring pressure — a meeting that always runs late, a commute you could shift, a task someone else could take.

• Keep moving most days. Regular aerobic activity goes with fewer sick days in observational research.

• Reduce exposure where it is realistic. Handwashing after the commute and before eating, airing rooms, and staying home when you are ill so you do not restart the cycle for others.

• Check vitamin D only if there is reason to. The benefit was concentrated in people who were very deficient; a test tells you which group you are in.

• Stay up to date with recommended vaccines, such as the seasonal flu vaccine, and ask your doctor which ones apply to you.

What does not help much is chasing every new supplement, or blaming yourself for each cold. Most adults get a few colds a year whatever they do.

Living with frequent colds: the questions people ask next

Once you have a sense of why you keep getting sick, the practical questions start. Here are short answers, with what the evidence can and cannot say.

Should I exercise when I keep getting sick?

Regular exercise goes with fewer colds, so getting sick often is not a reason to stop moving. In a study of 1,002 adults, those doing aerobic exercise on 5 or more days a week had 43% fewer days with upper respiratory infections over 12 weeks than those who were largely sedentary (doi.org). That was observational, so it shows an association rather than proof. A practical approach while you are actually ill is to rest, and to return gradually once a fever has gone. If you notice that you only get sick after races or very hard training blocks, mention that pattern to your doctor and look at your sleep and recovery in the weeks around them.

Does drinking alcohol make me get sick more often?

The studies in this article do not answer that directly. In the 1991 stress study, alcohol consumption did not explain why stressed people caught more colds (doi.org). What is clearer is the sleep link: shorter nights went with more colds in two viral-challenge studies (doi.org), and evenings of drinking often mean later bedtimes and lighter sleep. A practical approach is to note drinking nights alongside sick days for a couple of months and see whether they line up, and to bring that record to your doctor if they do.

Does vitamin D help if I keep getting sick?

Vitamin D may help some people who keep getting sick, mostly those who are very low in it. A meta-analysis of 25 trials found a small overall reduction in acute respiratory infections, with a much larger effect in people whose starting levels were below 25 nmol/L (adjusted odds ratio 0.30 in that group, among those taking daily or weekly doses) (doi.org). For people starting above that level, the benefit was smaller, and large occasional doses did not show the same benefit. A practical approach is to ask your doctor whether testing your vitamin D level makes sense, and to follow their advice on any supplement rather than self-dosing.

Why do I feel sick all the time but never actually get a cold?

Feeling sick all the time — run-down, achy, foggy, a little feverish-feeling — without clear infections is a different question from catching frequent colds. It can come from chronic short sleep, a long stretch of stress, low iron, thyroid problems, allergies, anxiety, or a post-viral illness that has not cleared. Persistent exhaustion that gets worse after effort and lasts months deserves its own look. If this started after COVID-19, read about long COVID symptoms. In either case, a practical approach is to list your symptoms, when they began and what makes them better or worse, and take that to a primary care doctor.

Is getting sick often a sign of something serious?

Usually not. Most adults who keep getting sick are catching ordinary colds from the people around them, at a rate near the CDC average of two to three a year (CDC). What raises concern is the type of infection, not only the number: two or more sinus or ear infections in a year, pneumonia more than once, infections that need intravenous antibiotics, deep abscesses or persistent thrush. These are among the Jeffrey Modell Foundation's warning signs of primary immunodeficiency, which affects about 1 in 500 people (Jeffrey Modell Foundation). Two or more signs is the threshold the foundation gives for talking to a physician.

What kind of doctor should I see if I keep getting sick?

A primary care doctor is the right first stop for most adults who keep getting sick. They can look at the overall pattern, check for common medical causes and decide whether blood tests are needed. A practical approach is to ask whether a full blood count, iron studies, thyroid tests or a blood sugar test make sense for you. If your infections fit the warning signs of immunodeficiency — repeated sinus, ear or chest infections, or infections that are hard to clear — the Jeffrey Modell Foundation strongly suggests consultation with primary immunodeficiency experts (Jeffrey Modell Foundation). In the US, that may mean a referral to an allergist-immunologist.

I'm embarrassed about calling in sick again. Is that normal?

Feeling embarrassed or guilty about calling in sick again is very common, and it is understandable — especially in workplaces that treat stamina as a virtue. But catching colds is linked to exposure, sleep and stress — viral-challenge studies tie higher stress and short sleep to more colds (doi.org) — not to toughness. Getting sick often doesn't make you weak or unreliable. Staying home while you are contagious also protects colleagues from the same cycle. If you keep getting sick and it is affecting your work, a note of dates and how long each illness lasted is useful both for your doctor and for an honest conversation with a manager.

How to bring this up with your doctor

Most people who keep getting sick never need specialist tests. It is still worth booking a visit if colds feel more frequent than your circumstances explain, if illnesses last longer or hit harder than they used to, or if any of the warning signs above apply.

What to track for a few months:

• Dates and length of each illness. Memory compresses — "I'm always sick" may turn out to be four colds in six months, or one long illness.

• What kind of illness it was: a cold, a sinus infection, an ear infection, a chest infection, a stomach bug, a skin infection.

• Whether you needed antibiotics, how many courses, and whether any were intravenous or in hospital.

• Fever, and how many days it lasted.

• What was going on before: short nights, a stressful stretch, travel, a sick child at home, a new job.

• Everything you take, including supplements and any medicines that affect the immune system.

What to say: "I've had [number] infections since [month]. Most were [type], and they lasted about [days]. I'm sleeping about [hours] a night and things have been [stressful/calm]. I'd like to know whether this is more than bad luck." It gives frequency, type and context without jumping to a conclusion.

What to ask:

• "Is this number of infections within the normal range for someone in my situation?"

• "Could anything I take, or any condition I have, be making me more prone to infections?"

• "Are blood tests worth doing — for example a blood count, iron, thyroid or blood sugar?"

• "Could allergies explain some of what I'm calling colds?"

• "Do my infections fit any of the warning signs for an immune problem, and would an immunologist be helpful?"

If you feel brushed off, it is reasonable to say: "I understand most adults get a few colds a year. I'd like to check whether my pattern fits that, because it's affecting my work and sleep." Bringing a written timeline makes that conversation much easier.

Before you blame yourself, check what your body already recorded

People who keep getting sick often carry a quiet verdict about themselves. My immune system is useless. I'm weaker than everyone else. I should be able to handle this. Others sometimes reinforce it with a joke about being "sick again".

Look at the order of events instead of the verdict. Colds rarely arrive out of a calm, well-rested month. Looking back, there is usually something visible first: a week of nights under 6 hours, a deadline that ran for a month, a child who brought home every virus from daycare, a trip with an early flight and a late return. The research above points in exactly that direction — short sleep and higher stress before exposure went with more colds in controlled studies, and living with young children meant weeks more of virus exposure each year.

That is not weakness; it is load and exposure. A body that slept 5 hours a night for a fortnight and spent it surrounded by sneezing people is doing what bodies do. It says nothing about your character or your willpower.

So give yourself permission, and pick one lever. Not ten. For most people, the most reachable one is sleep: a steady bedtime that gets you past 6 hours on weeknights. For others it is a single recurring pressure point, or easing off in the week before a holiday rather than sprinting into it. Change that one thing and then watch the trend for 1–2 weeks: how your nights look, how your stress load looks, how you feel. Over a few months, the number of sick days tells you more than any single cold — and it is a lot kinder than treating each cold as a personal failing.

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How Welltory helps — and what it cannot do

The limits first: Welltory is a general wellness product, not a medical device, and it does not detect, diagnose, predict or treat infections or immune problems. It holds no regulatory clearance and cannot tell you whether you have a cold, flu or an immune problem. What it can show is the part memory handles badly: how you slept and how loaded you were before you got sick.

Mark the illness when it happens. When a stress episode appears on your Today screen (iOS, with Apple Watch or Oura) and Welltory asks "What happened?", you can tap a suggested tag, type a few words or just talk. Use that moment to log the illness in your own words — "sore throat", "cold", "fever", "sinus" — along with anything relevant, such as "kid sick", "flight" or "deadline". Tags only count when they are attached to a stress or rest episode, not from standalone journal entries, so add them when an episode card appears.

Look at the days and weeks before. For each illness, look back at your sleep, stress minutes, Battery, resting heart rate and heart rate variability (HRV). Two questions matter: did a run of short nights or a high-stress stretch come first, and how did your numbers look in the 1–3 days before you felt ill? Studies of smartwatch data have found that resting heart rate can rise around the start of an infection: in a 2020 study, 26 of 32 people who caught COVID-19 (81%) showed changes in heart rate, daily steps or time asleep (doi.org). That is a research finding, not a Welltory feature, and a late night, alcohol or a hard workout move resting heart rate too. A change on its own tells you nothing certain about illness; note it alongside how you feel, and do not treat it as a verdict.

Let My Patterns do the sorting. Patterns start to become visible at around 7 tagged events, and insights need at least 7 occurrences of a tag in the current month, with some history from the month before. My Patterns then shows which tagged situations tend to come before stressful stretches, which rare tags your body responds to strongly, and every episode in which a tag appeared, with date and duration. If "short night", "flight" or "deadline" keeps turning up near your illness tags, that is the lever to try first.

Build a personal log for your doctor. The list of episodes tagged "cold" or "fever", with their dates, is a ready timeline of how often you have been ill. Add how many days each illness lasted, the type of infection and any antibiotics in your own notes. From the Welltory web app you can export your data as a CSV file (Dashboard → choose a chart → Export) to share.

Two caveats. These signals are non-specific: illness, alcohol, travel and a hard week move them in similar ways, so look across months rather than single days. And if checking the data starts to feel like another way to worry, check less. The patterns you find are associations to discuss with your doctor, not proof of why you keep getting sick.

How we made it

Made with AI tools, then edited and fact-checked by the Welltory team. See our Editorial & AI policy.

Data analysis by Jane Smorodnikova, co-founder of Welltory and the person who built the methodology behind how we read physiological data.

Written by Tatsiana Yashyna.

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