Many things can affect how your body responds to a symptom and what kind of care you may need. These include:

• Your age. Babies and older adults tend to get sicker quicker.
• Your overall health. If you have a condition such as diabetes, HIV, cancer, or heart disease, you may need to pay closer attention to certain symptoms and seek care sooner.
• Medicines you take. Certain medicines, such as blood thinners (anticoagulants), medicines that suppress the immune system like steroids or chemotherapy, herbal remedies, or supplements can cause symptoms or make them worse.
• Recent health events, such as surgery or injury. These kinds of events can cause symptoms afterwards or make them more serious.
• Your health habits and lifestyle, such as eating and exercise habits, smoking, alcohol or drug use, sexual history, and travel.

If you're not sure if a child's fever is high, moderate, or mild, think about these issues:

With a high fever:

• The child feels very hot.
• It is likely one of the highest fevers the child has ever had.

With a moderate fever:

• The child feels warm or hot.
• You are sure the child has a fever.

With a mild fever:

• The child may feel a little warm.
• You think the child might have a fever, but you're not sure.

Certain health conditions and medicines weaken the immune system's ability to fight off infection and illness. Some examples in children are:

• Diseases such as diabetes, cystic fibrosis, sickle cell disease, and congenital heart disease.
• Steroid medicines, which are used to treat a variety of conditions.
• Medicines taken after organ transplant.
• Chemotherapy and radiation therapy for cancer.
• Not having a spleen.

Temperature varies a little depending on how you measure it. For children up to 11 years old, here are the ranges for high, moderate, and mild according to how you took the temperature.

Oral (by mouth), ear, or rectal temperature

• High: 104° F (40° C) and higher
• Moderate: 100.4° F (38° C) to 103.9° F (39.9° C)
• Mild: 100.3° F (37.9° C) and lower

A forehead (temporal) scanner is usually 0.5° F (0.3° C) to 1° F (0.6° C) lower than an oral temperature.

Armpit (axillary) temperature

• High: 103° F (39.5° C) and higher
• Moderate: 99.4° F (37.4° C) to 102.9° F (39.4° C)
• Mild: 99.3° F (37.3° C) and lower

Note: For children under 5 years old, rectal temperatures are the most accurate.

Babies can quickly get dehydrated when they lose fluids because of problems like vomiting or fever.

Symptoms of dehydration can range from mild to severe. For example:

• The baby may be fussy or cranky (mild dehydration), or the baby may be very sleepy and hard to wake up (severe dehydration).
• The baby may have a little less urine than usual (mild dehydration), or the baby may not be urinating at all (severe dehydration).

You can get dehydrated when you lose a lot of fluids because of problems like vomiting or fever.

Symptoms of dehydration can range from mild to severe. For example:

• You may feel tired and edgy (mild dehydration), or you may feel weak, not alert, and not able to think clearly (severe dehydration).
• You may pass less urine than usual (mild dehydration), or you may not be passing urine at all (severe dehydration).

Severe dehydration means:

• The baby may be very sleepy and hard to wake up.
• The baby may have a very dry mouth and very dry eyes (no tears).
• The baby may have no wet diapers in 12 or more hours.

Moderate dehydration means:

• The baby may have no wet diapers in 6 hours.
• The baby may have a dry mouth and dry eyes (fewer tears than usual).

Mild dehydration means:

• The baby may pass a little less urine than usual.

Severe dehydration means:

• The child's mouth and eyes may be extremely dry.
• The child may pass little or no urine for 12 or more hours.
• The child may not seem alert or able to think clearly.
• The child may be too weak or dizzy to stand.
• The child may pass out.

Moderate dehydration means:

• The child may be a lot more thirsty than usual.
• The child's mouth and eyes may be drier than usual.
• The child may pass little or no urine for 8 or more hours.
• The child may feel dizzy when he or she stands or sits up.

Mild dehydration means:

• The child may be more thirsty than usual.
• The child may pass less urine than usual.

Many nonprescription and prescription medicines can cause nausea or vomiting. A few examples are:

• Antibiotics.
• Antidepressants.
• Aspirin, ibuprofen (such as Advil or Motrin), and naproxen (such as Aleve).
• Medicines used to treat cancer (chemotherapy).
• Opioid pain medicines.
• Vitamins and mineral supplements, such as iron.

Starting a new medicine or increasing the dose can cause nausea and vomiting. Nausea and vomiting also may mean that there is too much medicine in your body, even if you took it properly.

Repeated vomiting: The child vomits nearly every time he or she tries to drink something. This type of vomiting makes it impossible to keep down any fluids or solid food, which greatly increases the chance of becoming dehydrated. The child has an even greater chance of dehydration if he or she also has diarrhea.

Occasional vomiting: Some young children vomit every once in a while for no clear reason. This usually does not increase the risk of dehydration or other problems as long as the child can keep down fluids between vomiting. The more time that passes between episodes of vomiting, the less serious it probably is. But if the vomiting continues, it may be important to find the cause.

Symptoms of serious illness in a baby may include the following:

• The baby is limp and floppy like a rag doll.
• The baby doesn't respond at all to being held, touched, or talked to.
• The baby is hard to wake up.

Symptoms of serious illness may include:

• A severe headache.
• A stiff neck.
• Mental changes, such as feeling confused or much less alert.
• Extreme fatigue (to the point where it's hard for you to function).
• Shaking chills.

An illness plan for people with diabetes usually covers things like:

• How often to test blood sugar and what the target range is.
• Whether and how to adjust the dose and timing of insulin or other diabetes medicines.
• What to do if you have trouble keeping food or fluids down.
• When to call your doctor.

The plan is designed to help keep your diabetes in control even though you are sick. When you have diabetes, even a minor illness can cause problems.

It is easy for your diabetes to become out of control when you are sick. Because of an illness:

• Your blood sugar may be too high or too low.
• You may not be able take your diabetes medicine (if you are vomiting or having trouble keeping food or fluids down).
• You may not know how to adjust the timing or dose of your diabetes medicine.
• You may not be eating enough or drinking enough fluids.

Colic is an extreme type of crying in a baby between 3 weeks and 3 months of age. All babies cry, but a colicky baby will cry for hours at a time, no matter what you do.

During a crying episode, a colicky baby may cry loudly and continuously and be hard to comfort. The baby may get red in the face, clench the fists, and arch his or her back or pull the legs up to the belly.

A baby that is extremely sick:

• May be limp and floppy like a rag doll.
• May not respond at all to being held, touched, or talked to.
• May be hard to wake up.

A baby that is sick (but not extremely sick):

• May be sleepier than usual.
• May not eat or drink as much as usual.