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What are Common Causes of Fever and Weakness?

By B. Miller
Updated May 17, 2024
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Fever and weakness are typically caused by an infection or illness in the body. Common illnesses that lead to fever and weakness include the flu and chicken pox, among others. Viral or bacterial illnesses can cause a fever and lead one to feel weak; in addition, any infection, even a small one, can be a cause of a fever. This means that a low-grade fever can be indicative of an infection, even if one is unaware of an infection in the body. Because these symptoms are so common, a doctor may need to do a blood test or throat swab to determine what type of illness is present.

In most cases, there is no treatment for a viral illness that causes fever and weakness. Antibiotics are ineffective against viral illnesses, though it may be a good idea to visit a doctor anyway to be sure that the cause of the fever is not anything serious. Generally, a virus will cause a lower grade fever than a bacterial infection, but this is certainly not always the case. The fever should not last more than a few days, and usually getting some rest and drinking plenty of fluids is an effective treatment for mild illnesses.

A bacterial infection that causes fever and weakness can usually be treated by antibiotics. Again, virtually any infection can cause a fever; it is also possible for any infection to spread quickly, so it is necessary to keep a close eye on it, and visit a doctor if it worsens. If one has an infection from a cut on the skin, for example, and is experiencing fever and weakness, it is a good idea to visit a doctor. In addition, any skin infection with red streaks coming off it has entered the bloodstream, which can cause septic shock and death; one should immediately get emergency treatment and intravenous antibiotics.

Experts are occasionally divided as to whether medication should be taken to lower a fever. If the fever is high, or the person with the fever is elderly or very young, medication should be given to reduce the fever. On the other hand, if it is a relatively low-grade fever and the person is otherwise in good health, it may be best to allow the fever to run its course; the fever is the body's way of fighting off an infection, and it can actually be helpful. Fevers naturally cause fatigue and weakness, so if it is possible for one to just get some rest until one recovers, that can often be the best method of treatment.

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Discussion Comments

By anon332376 — On Apr 28, 2013

I have been to the doctor two weeks ago, and she said to drink plenty of fluids. I have had a fever of 99.9 to 101 for the past two weeks. I am not sick, throwing up, nor do I have diarrhea.

I have had thyroid cancer and colon cancer in the past five years and been cancer free for the past two years. I never get sick or run a temp so this concerns me. I have no idea what could be going on. I don't go to the doctor at the drop of a hat because I hate sitting and waiting. If my body doesn't fight anything off within a week, that is when I go see the doc. What can cause a temp out of the blue with no sickness?

By anon317149 — On Jan 31, 2013

I've had a fever for six days now. It got up to 104.5 but has stayed around 102 to 103 for the most part. I go to the doctor and they tell me to go home and drink water. They don't spend more than five minutes with a person and then charge you 200 bucks. Guess I'll just stay home and die in my sleep.

By anon316415 — On Jan 28, 2013

I have had a fever for almost two years now -- a Low grade fever. It normally runs from 99 to 101 every day of my life. No doctor I have seen can figure out why and says its OK. I'm not a college professor but I don't think its OK to run a fever for that long and not know why.

I have been treated for h. pylori in the past. I do have to take iron transfusions about once a year my body won't absorb the iron. If anyone sounds like this and can help me, reply please.

By anon301757 — On Nov 05, 2012

I am very dizzy and disoriented. I have a fever, and I am not able to get up or walk around.

By Oceana — On Jul 04, 2012

Strep throat will give you a fever and causes you to become weak within a few hours. Mine started out as just a slightly swollen throat, but by the end of the day, I could barely swallow, and I had a fever of 100 degrees.

I also felt really out of my head. It was hard for me to walk to the bathroom, because the fever had made me weak.

I took acetaminophen to bring it down, but I had to see the doctor for some antibiotics. Since strep is a bacteria, it worked at knocking out the infection. I also got a steroid shot to boost my immune system.

Strep is something that you don't want to mess with. I really felt like my throat would close up that night. I was so glad to get medication for it, because I started feeling better the day after starting the drugs.

By lighth0se33 — On Jul 04, 2012

I had a urinary tract infection that festered and became a kidney infection. The two main signs of this were fever and frequent urination.

Every urinary tract infection manifests with frequent urination, but you don't usually have a fever with one. However, if you do like I did and wait a couple of weeks in hopes that it will go away, then you will likely develop a kidney infection, which does cause a fever.

I also vomited a bit, and this made me weak. Once I threw up, I knew that it was time to give in and see the doctor. I was so weak that day that my husband had to carry me to the car.

By orangey03 — On Jul 03, 2012

@kylee07drg – That sounds intense! I've had fever and weakness before, but I've never had vomiting and diarrhea that often at the same time.

I have had the flu twice in my life, so I have learned what to look for. I get a fever, along with joint pain and weakness. It's always for no reason, too. I could understand the weakness and pain if I had just run a marathon or something, but when it happens out of the blue and is accompanied by a fever, I know that I have come down with the flu.

I haven't had the flu in years, likely because I always get a flu shot. I don't want to go through that misery again.

By kylee07drg — On Jul 02, 2012

I had a high fever and pain in my abdomen as a child, and shortly after developing these symptoms, I began vomiting. I also experienced severe diarrhea. I quickly became too weak to sit up because of this.

My parents feared that I would become dehydrated, because I was going to the bathroom to evacuate both ends nearly every thirty minutes. They took me to the hospital, where I learned that I had rotavirus.

There was no treatment, so I just had to stay in the hospital for a week. They pumped me full of intravenous fluids to keep me hydrated, and I got occasional shots to stop the vomiting and diarrhea.

Even after being released, I was weak for days. It takes some time to recover from an ordeal like that.

By TreeMan — On Jul 02, 2012
@jmc88 - I think your story also shows that paying attention to things that may potentially cause illnesses is also part of being responsible for your health. I have met people who have gotten food poisoning and couldn't even remember what they had eaten the day before to track what may have caused it.

I know when I was in college, meningitis was a big deal. I am pretty sure colleges are still pretty active in getting people vaccinated against the bacterial form of the disease. One of the main symptoms of meningitis, though, is swelling around the neck that makes it difficult to move your head. I think knowing things like that is important for anyone who may be at increased risk for the disease, because recognizing the symptoms means you can get help faster.

I love the online resources where you can put in your symptoms and get a list of possible illnesses. It's important for people to read carefully about them, though, and not immediately assume they have the worst possible illness.

By jmc88 — On Jul 01, 2012

@jcraig - Good advice. To go along with that, I think something else people should think about when they have a fever and other symptoms of illness is what else it could be besides a basic cold. You should start thinking back over things that have happened lately and see if there could be any links between the illness and some other event.

I work in the woods a lot, and some time last year, I started getting a fever and some of the other typical symptoms of the flu. Luckily, it was the summer, so it was unlikely that it was the flu. I remembered that a week or so before that I had gotten bitten by a tick. I hadn't thought a lot about it, since it has happened quite a few times before. I looked at the bite again, and sure enough, there was a pretty big rash forming.

I went to the doctor and told her the symptoms and showed her the bite. Given everything that had happened, it was pretty clear that the tick had caused the illness. It actually wasn't Lyme disease, though. It was called Master's disease, which is a related bacterial infection caused by a different kind of tick.

By jcraig — On Jun 30, 2012

@JimmyT - I agree with you for the most part. I know a lot of people who run to the doctor at the first sign of sickness when it is unnecessary a great deal of the time. They do the same with their kids. I understand that children have weaker immune systems than adults, but by the time they get to be a few years old, a kid doesn't need to see a doctor every time he has a basic cold or slight fever. There's very little a doctor can do in those cases that bed rest won't fix on its own.

The time I do think it is important to see a doctor is if you have more than the symptoms of a basic cold or the flu or something. My general rule of thumb is that if I am experiencing symptoms above and beyond a mild fever, it's time to see a doctor. For example, high fevers can lead to death, so those should definitely be checked out. The same can be said about excessive vomiting or problems stemming from excessive weakness and fatigue.

By JimmyT — On Jun 30, 2012

I think the best advice if you have a fever and tiredness is just what the article suggests. Wait a couple of days and then go to the doctor if it doesn't get any better. I think a lot of people start jumping to conclusions when they have a fever and think that something horrible is happening to them. Anyone can get sick, and most healthy people can fight off infections on their own. It just takes the body a few days to make it happen.

I hardly ever get sick, but it seems like about once a year in March I will start getting a fever that lasts for a couple of days and then goes away. I never feel the need to go to the doctor. I just hole up in my bed and rest while drinking a lot of fluids and healthy food. I think if a lot of people would just wait a couple more days before going to the doctor that they would find the body can fight off infections without antibiotics.

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