Nadir: A Common Side Effect of Chemotherapy

Nadir is a term that refers to the lowest point of anything. In medical terms, nadir could mean the lowest concentration of a drug in the body. With regard to chemotherapy specifically, it describes the point at which blood cell counts are at their lowest after a chemotherapy treatment. It is commonly referred to as the "nadir period" or simply "nadir" among healthcare workers and patients.

Illustration of red and white blood cells
Ryan Etter / Ikon Images / Getty Images

Why Nadir Occurs

While chemotherapy directly targets cancer cells, it also affects other normal rapidly dividing cells in the process, including those found in the gut, lining of the mouth, hair, and bone marrow where the blood cells are produced.

During chemotherapy bone marrow activity may be decreased, resulting in lowered blood cell counts within the body, including red blood cells, white blood cells, and platelets.

With each chemotherapy treatment comes a nadir period, so people who have more frequent treatments may experience lowered counts more often than those whose treatments are spaced further apart.

Timeline and Risks

Each blood cell type reaches nadir at different times. Low counts have varying effects as well.

Because permanent damage to bone marrow can occur if chemotherapy is given too often, this is taken into account when determining a chemotherapy schedule. The next dose of chemotherapy should be given only after a person's blood counts have increased to safe levels after the nadir period. This happens gradually and typically takes about three to four weeks.

White Blood Cells

White blood cells (WBCs) generally drop to their lowest count about seven to 14 days after a chemotherapy treatment.

WBCs, especially a specific type called neutrophils, are a vital component of the immune system as they keep invading bacteria at bay. Because of this, you are at a heightened risk of developing infections when counts are low.

A normal neutrophil count is 2,500 to 6,000. Lower than that and the immune system is said to be compromised—and the risk of infection increases. If neutrophils are abnormally low, below 500, the condition is called neutropenia, and serious infection can occur.

Red Blood Cells

Red blood cells (RBCs) generally live longer than white blood cells and reach a nadir period several weeks after treatment. Their job is to carry oxygen from the lungs to tissues throughout the body.

RBCs contain hemoglobin, an iron-rich protein that transports oxygen and also gives blood its red color. When red blood cell counts are too low, the result is called anemia.


Platelets generally reach their nadir period at about the same time as white blood cells. Platelets serve an important function by helping blood to clot, which prevents bleeding.

When the number of platelets in the body fall too low, the condition is called thrombocytopenia. It is marked by bruising, nosebleeds, excessive bleeding from cuts, and fatigue. A reddish-purple skin rash that looks like small dots is also a symptom of a low platelet count.

Managing Lowered Blood Cell Counts

When blood counts become too low, WBCs, RBCs, and platelets can be increased through drugs that boost cell production, as well as through transfusions. Upping your consumption of certain healthy meats, fruits, and vegetables can also help boost the body's natural production of blood cells.

Protein sources like poultry and fish may promote the production of WBCs. Platelets can be increased by eating foods rich in vitamins B-9 and B-12.

The following vitamins and minerals help increase the body's production of RBCs. Consider adding supplements and/or eating foods that are rich in the following:

  • Iron: Found in leafy green vegetables like kale and spinach, organ meats, lean red meat, egg yolks, beans, and legumes
  • Vitamin A (retinol): Found in cod liver oil, sweet potatoes, spinach, broccoli, black eyed peas, carrots, squash, pumpkin, cantaloupe, mango, and apricots
  • Vitamin B-6 (pyridoxine): Found in salmon, poultry, eggs, potatoes, sweet potatoes, bananas, avocado, pistachios, peanuts, whole grains, and brown rice
  • Vitamin B-9 (folate): Found in citrus fruit, banana, papaya, beets, asparagus, Brussels sprouts, avocado, walnuts, and flax seeds
  • Vitamin B-12 (cobalamin): Found in organ meat, beef, tuna, trout, salmon, sardines, clams, and eggs
  • Vitamin C: Found in citrus fruit, cantaloupe, kiwi, papaya, strawberries, sweet potatoes, tomatoes, bell peppers, broccoli, cauliflower, and kale
  • Copper: Found in shitake mushrooms, spirulina, almonds, cashews, sesame seeds, lobster, oysters, organ meats, Swiss chard, spinach, and kale
  • Vitamin E: Found in salmon, trout, shrimp, goose, spinach, broccoli, turnip greens, squash, avocados, wheat germ oil, olive oil, sunflower seeds, almonds, hazelnuts, pine nuts, peanuts, brazil nuts, mango, and kiwi

Precautions to Take During Nadir

It's important to avoid infection or any activities that could induce bleeding, as WBCs that fight infection and platelets that help with clotting are diminished. Follow some simple tips including:

  • Washing hands often
  • Thoroughly washing and cooking food before consuming
  • Avoiding contact with those who may carry an infection, as well as pet waste
  • Avoiding getting scratches or cuts

Help boost your immune system by:

  • Getting enough sleep
  • Eating a healthy, balanced diet rich in fruits and vegetables
  • Avoiding caffeine and alcohol
  • Drinking plenty of water

When to See a Doctor

Seek immediate medical attention if you have bleeding that won't stop or a fever of 100 degrees or higher, as that could indicate the presence of a serious infection.

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7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. The American Cancer Society. Chemotherapy for liver cancer.

  2. The American Cancer Society. Chemotherapy for acute myeloid leukemia (AML).

  3. Canadian Cancer Society. Low blood cell counts.

  4. The American Cancer Society. Understanding your lab test results.

  5. The American Cancer Society. Low blood counts, fever, and infections.

  6. The American Cancer Society. Low red blood cell counts (Anemia).

  7. Harvard Health Publishing. How to boost your immune system.

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