When to Call the Doctor During Cancer Treatment

Approved by the Cancer.Net Editorial Board, 12/2016

Cancer and cancer treatments may cause side effects that need medical attention. However, it can be hard to know when to call the doctor. It is important to ask your doctor which signs and symptoms to expect, and which ones need medical attention right away.

Some serious side effects that need medical attention include:

  • Infections
  • Deep vein thrombosis (DVT), which is a potentially life-threatening blood clot
  • Pulmonary embolism (PE), which is a blood clot in the lung and a medical emergency
  • Tumor lysis syndrome (TLS), which is a life threatening vital organ injury


Cancer and its treatments may make it more likely that you will develop an infection. An infection occurs when bacteria, viruses, or less often, fungi (such as yeast) invade the body, but the immune system cannot stop them fast enough. Cancer treatments may weaken the immune system, increasing the chance of an infection. For example, chemotherapy lowers the number of neutrophils. Neutrophils are a type of white blood cell that helps fight infection.

Common types of infections that need immediate medical attention include:

  • Pneumonia, which starts in the lungs

  • Urinary tract infection, which can start in the bladder or kidneys

  • Infections in the mouth, throat, esophagus, stomach, intestines, or anus

  • Blood infections, which are most common in patients with low white blood cell counts or implanted catheters

Infection during cancer treatment can be life threatening. Your doctor will help you determine if the infection is serious and how best to manage your symptoms.

Symptoms of infection requiring immediate care

Patients experiencing these symptoms may need emergency care. Call your doctor right away if you have one or more of the signs listed below. If your symptoms cannot be assessed right away, you may need to go to the emergency room.

  • Fever that is 100.5° F (38° C) or higher

  • Shaking chills

  • Chest pain or shortness of breath

  • Confusion

  • Severe headache with a stiff neck

  • Bloody or cloudy urine

Symptoms of infection requiring prompt care

The symptoms listed below may be safely managed by visiting your doctor’s office.

  • Cough

  • Swelling or redness anywhere, including around a cut, wound, or catheter

  • Sores or white coating in your mouth or on your tongue

  • Tooth or gum pain

  • Sore throat

  • Ear pain

  • Headache or bad sinus or facial pain

  • Stiff or sore neck

  • Abdominal pain

  • Skin sores or rash

  • Diarrhea or sores near the anus

  • Bloody or cloudy urine

  • Pain or burning when urinating

  • Vaginal discharge or itching

  • Any change or something that feels not normal for you, including a general sense of feeling unwell

Preventing infections

To help prevent infections follow the tips listed below.

  • Wash your hands well and often or use antibacterial hand sanitizers. Always clean your hands before eating and after using the restroom.

  • Avoid contact with people who are sick or recently ill. Let your doctor know if you have been around someone who is visibly sick.

  • Avoid big crowds when possible

  • Avoid sharing food, drinks, utensils, and personal items

  • Shower or bathe daily and apply lotion to prevent dry cracked skin

  • Clean teeth and gums with a soft toothbrush

  • Avoid cuts and use an electric razor if possible

  • Avoid cat litter and handling animal waste

  • Keep the area around any catheter(s) clean and dry

  • Follow food safety guidelines, including no raw or undercooked meats, fish, shellfish, or poultry and washing all fresh fruits and vegetables

  • Eat a variety of nutritious foods

  • Get at least 7 to 8 hours of sleep

  • Get enough physical activity

  • Avoid people who have just had vaccines for chicken pox, measles, polio, or the mist type of flu vaccine

  • Check with your doctor before getting any shot or vaccine yourself

DVT and PE

Thrombosis is a blood clot inside a blood vessel. DVT occurs when a blood clot forms inside a vein deep in the body, usually in a leg. DVT can be treated with drugs called anticoagulants. A blood clot may go away naturally, but a DVT requires anticoagulant treatment because it can become life threatening if the clot travels to the lungs and causes a PE. A PE is a blockage of one or more of the lung’s major arteries.

The signs and symptoms of DVT might be related to DVT itself or to a PE. Some people aren't aware of a deep vein clot until they have signs and symptoms of PE. See your doctor right away if you have signs or symptoms of either condition. Both DVT and PE can cause serious, possibly life-threatening problems if not treated.

Signs and symptoms of a DVT may include one or more of these:

  • Swelling of the leg or along a vein in the leg or arm

  • Pain or tenderness in the leg, which you may feel only when standing or walking

  • Pain or tenderness in the arm that limits movement

  • Increased warmth in the area of the leg or arm that's swollen or painful

Signs and symptoms of a PE may include one or more of these:

  • Red or discolored skin on the leg or arms

  • Unexplained shortness of breath

  • Pain in the chest, sides, or back with deep breathing

  • Coughing up blood

  • Fast breathing rate

  • Fast heart rate

Factors that may increase the risk of getting a DVT:

  • Diagnosis of adenocarcinoma  

  • Surgery

  • Chemotherapy

  • Hormonal therapy

  • Not being able to move for a long time

  • Personal or family history of blood clotting disorders

  • Medical conditions such as heart disease or lung disease

  • Increased age

  • Smoking

To help prevent blood clots:

  • Get out of bed and move around as soon as you can after surgery or illness.

  • Get up from your seat and flex your muscles periodically when traveling or sitting for long periods.

  • If you have had DVT before, ask your doctor about wearing compression stockings while traveling and/or taking blood-thinning medication before a trip.

Also ask your doctor about your risk of developing a blood clot or DVT and what you can do to help prevent them. Learn more about bleeding and clotting problems and ASCO’s recommendations for preventing and treating blood clots.


TLS is a life-threatening medical emergency. It usually occurs after chemotherapy for a fast-growing cancer, such as some types of leukemia or lymphoma. TLS is less likely to develop in people with solid tumors, with the exception of small cell lung cancer. Talk with your doctor about your risk of TLS.

The cause of TLS is the rapid death of cancer cells caused by cancer treatment. As tumor cells die, they break apart and spill their contents into the blood. Tumor cell contents include potassium, phosphate, and tumor DNA. This sudden release of contents causes a change in certain electrolytes and other chemical concentrations in the blood, which can damage organs, including the kidneys, heart, liver, and nervous system. The result can be loss of muscle control, seizures, and death. 

Although TLS is usually linked with chemotherapy, other types of cancer treatment may lead to TLS. Rarely, this syndrome may occur before starting any cancer treatment, and very rarely after a biopsy of a tumor. Patients with the highest risk of TLS receive cancer treatment in the hospital. This is so that doctors can monitor them and deliver intravenous (IV) fluids and medications that lower uric acid such as rasburicase (Elitek) to help prevent TLS. This syndrome can be found through blood and other laboratory tests and specific physical signs and symptoms (see below).

Types of cancers most commonly linked with TLS include:

  • Burkitt lymphoma

  • Large-cell lymphoma (types of non-Hodgkin lymphoma)

  • Acute lymphocytic leukemia

  • Acute myeloid leukemia

  • Chronic lymphocytic leukemia

  • Small cell lung cancer

The following factors may also increase a person’s risk of TLS during cancer treatment:

  • High white blood cell level

  • High blood uric acid level

  • Kidney problems 

  • Dehydration

  • Late stage of cancer

  • Large tumor amount

The signs and symptoms of TLS include:

  • Nausea

  • Vomiting

  • Diarrhea

  • Swelling

  • Shortness of breath

  • Irregular heartbeat

  • Low blood pressure

  • Cloudy or bloody urine

  • Low urine output

  • Back pain behind the lower ribs

  • Weakness or low energy

  • Seizures

  • Muscle spasms or cramps

  • Pain in the joints

  • Sudden death

Talking with your health care team

Each type of cancer and cancer treatment causes different side effects, so ask your doctor what side effects you should watch for. Also discuss how and when to contact your doctor and other members of your health care team during your treatment. Ask your doctor the following questions:

  • What are the possible effects of my cancer?

    • Which of these should I call you for?

    • Which ones are considered an emergency that I should call 911 or go to the emergency room for?

  • What are the possible side effects of my cancer treatments?

    • Which of these should I call you for?

    • Which ones are considered an emergency that I should call 911 or go to the emergency room for?

  • Are there other situations when I should call you during treatment? What is your contact information?

  • When should I contact other members of the health care team? What is their contact information?

  • What telephone number should I call after normal business hours?

  • When can I expect a return call from you, the team, or the after hours on-call provider?

  • When should I use email to communicate with you and your staff?

More Information

Side Effects

Food Safety During and After Cancer Treatment

Additional Resources

National Cancer Institute: Infection (PDF)

CDC: Preventing Infection in Cancer Patients and Cancer, the Flu, and You

National Heart, Lung, and Blood Institute: What is Deep Vein Thrombosis? and What is a Pulmonary Embolism?