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, or natural health products 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.

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.

Temperature varies a little depending on how you measure it. For adults and children age 12 and older, these are the ranges for high, moderate, and mild, according to how you took the temperature.

Oral (by mouth) temperature

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

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

Ear temperature

• High: 40.6 °C (105 °F) and higher
• Moderate: 38.6 °C (101.4 °F) to 40.5 °C (104.9 °F)
• Mild: 38.3 °C (101 °F) and lower

Armpit (axillary) temperature

• High: 39.5° C (103° F) and higher
• Moderate: 37.5 °C (99.5 °F) to 39.4 °C (102.9 °F)
• Mild: 37.4° C (99.4° F) and lower

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

With a high fever:

• You feel very hot.
• It is likely one of the highest fevers you've ever had. High fevers are not that common, especially in adults.

With a moderate fever:

• You feel warm or hot.
• You know you have a fever.

With a mild fever:

• You may feel a little warm.
• You think you 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 adults are:

• Diseases such as diabetes, cancer, heart disease, and HIV/AIDS.
• Long-term alcohol and drug problems.
• Steroid medicines, which may be used to treat a variety of conditions.
• Chemotherapy and radiation therapy for cancer.
• Other medicines used to treat autoimmune disease.
• Medicines taken after organ transplant.
• Not having a spleen.

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:

• Your mouth and eyes may be extremely dry.
• You may pass little or no urine for 12 or more hours.
• You may not feel alert or be able to think clearly.
• You may be too weak or dizzy to stand.
• You may pass out.

Moderate dehydration means:

• You may be a lot more thirsty than usual.
• Your mouth and eyes may be drier than usual.
• You may pass little or no urine for 8 or more hours.
• You may feel dizzy when you stand or sit up.

Mild dehydration means:

• You may be more thirsty than usual.
• You may pass less urine than usual.

Severe vomiting can mean that:

• You vomit more than 10 times in 24 hours.
• For at least 24 hours, you vomit every time you try to drink something.
• The vomit shoots out in large amounts and with great force.

Many non-prescription 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.

Shock is a life-threatening condition that may quickly occur after a sudden illness or injury.

Adults and older children often have several symptoms of shock. These include:

• Passing out (losing consciousness).
• Feeling very dizzy or light-headed, like you may pass out.
• Feeling very weak or having trouble standing.
• Not feeling alert or able to think clearly. You may be confused, restless, fearful, or unable to respond to questions.

Shock is a life-threatening condition that may occur quickly after a sudden illness or injury.

Babies and young children often have several symptoms of shock. These include:

• Passing out (losing consciousness).
• Being very sleepy or hard to wake up.
• Not responding when being touched or talked to.
• Breathing much faster than usual.
• Acting confused. The child may not know where he or she is.

Symptoms of a heart attack may include:

• Chest pain or pressure, or a strange feeling in the chest.
• Sweating.
• Shortness of breath.
• Nausea or vomiting.
• Pain, pressure, or a strange feeling in the back, neck, jaw, or upper belly, or in one or both shoulders or arms.
• Light-headedness or sudden weakness.
• A fast or irregular heartbeat.

For men and women, the most common symptom is chest pain or pressure. But women are somewhat more likely than men to have other symptoms like shortness of breath, tiredness, nausea, and back or jaw pain.

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.