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In Cancer Treatment, what does "Nadir" Mean?

Mary McMahon
Updated Mar 03, 2024
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When a cancer patient reaches his or her “nadir,” it means that the patient's blood counts are the lowest they will be during treatment. Low blood counts cause a variety of symptoms including lethargy, but they also leave the patient highly susceptible to infection. For this reason, cancer treatments are carefully timed so that doctors know when to expect the nadir, and cancer patients are usually warned ahead of time about the risks of this period. After the nadir, the patient's blood count will start to rise, decreasing the risk of danger and hopefully heralding the return of good health.

In order to understand this condition, it may help to know what a “blood count” is. Blood counts are performed by taking a blood sample and using it to determine the levels of the various components of blood in the body, including white blood cells and red blood cells. Chemotherapy lowers blood counts by interfering with the production of new blood cells in the marrow of the bones, causing the blood count to decline because no more cells are being produced.

White blood cells are of special concern during chemotherapy, because they have the shortest lifespan in the blood, and they are the body's first line of defense against infection. When the blood count starts to decline, white blood cells usually lead the way, and the patient is left defenseless. As the body processes the chemotherapy, the stem cells in the bone marrow start dividing again and producing new blood cells, and the blood count will begin to rise.

Timing of chemotherapy is important. If a treatment is given when the stem cells are actively producing new white blood cells, it can result in long-term problems for the patient, including bone loss. Therefore, the blood is tested before a treatment is given to determine where the stem cells are in their production cycle, which takes around 28 days. If more than one treatment is planned in a cycle of chemotherapy, the second treatment is given before the stem cells have a chance to fully recover, ensuring that they will not be in active production.

The timing of this period varies, depending on the drug involved, but the range is usually seven to 14 days. During the nadir, patients must avoid any potential sources of infection, because even a common cold can turn very serious for a cancer patient with low blood counts. People also usually feel especially poorly during the nadir period, which is something friends and family may want to keep in mind.

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Mary McMahon
By Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a The Health Board researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Discussion Comments

By anon999295 — On Nov 29, 2017

Hello. I was told by my chemo nurse that the nadir was day ten. So does that mean that the white blood cell count starts recovering from day 11? When is it safe to go out again?

By amypollick — On Jun 24, 2013

@anon339557: No, you are not being a wuss or selfish. Most people who work the whole time during chemo usually have jobs that do not require them to expend a great deal of physical effort. A job at a nursing home is not one of those careers.

Look at it this way: if you did pick up some bug, you'd also be in a prime position to pass it along to the residents you work with, and that's no good, either. If you pick up a bug, then you become Typhoid Mary and everybody gets it. So staying home is not selfish. At all.

By anon339557 — On Jun 24, 2013

I also had a question on the nadir period. I just got done with my second chemo session. After the first one my counts dropped to 0. Now with this one they have me getting a neulasta shot after to prevent that, but I'm still nervous about being around crowds or out in public. I work in a nursing home and am taking this time off because I don't want to take a chance of picking anything up. Sometimes I feel guilty taking the time off especially when I read about people continuing to work through their chemo. Am I a wuss for taking the time off to fully care for myself? Am I selfish?

By anon282891 — On Aug 01, 2012

It is better to err on the side of caution and not take any chances. If she gets sick or an infection, it will delay her next chemotherapy, which will delay getting well. It's her life, so tell her not to take chances with it.

By JaneAir — On May 05, 2012

Although the nadir sounds kind of rough, at least the patient's blood cell counts start going up after the nadir is over, which decreases the likelihood of infection. It almost sounds like the nadir is the roughest part of the cancer, and then everything starts looking up after that.

However, I've never had cancer myself, so I might just be talking out of turn here. I imagine the reality of having cancer is much different than just reading an article about it or even witnessing family members go through it.

By SZapper — On May 04, 2012

I knew white blood cells defended against infection, but I didn't know they had the shortest lifespan in the blood. How unfortunate! And of course since they are the first to go, this makes the cancer patient more susceptible to infection.

I actually have a friend who has a lowered immune system, so I know how easy it is to get sick when you're not at 100%. My friend has caught several nasty infections that were even harder to treat because her immune system was down. I definitely feel sympathetic towards cancer patients when they're in the nadir of their treatment.

By bear78 — On May 03, 2012

As far as I know, in medical terms, nadir has more than one meaning. The word in general means "lowest point." This could be the lowest point for blood counts but it could be used to describe other things too.

For example, I'm being treated for thyroid dysfunction and my doctor uses "nadir" when he's talking about the lowest amount of medication in my body.

I think in some cancer related treatments, they use the term nadir also to show the risk for death in certain procedures. So a nadir is the lowest risk for mortality in that case.

By SteamLouis — On May 03, 2012

@fify-- Yes, the timing of nadir can change from person to person. Mine was not two weeks after starting treatment even though that's usually what they say. They say 10-15 days after the first day of chemotherapy. So you're better off having the doctor look at blood counts and figure that out for you.

I was working during my chemotherapy and whether I liked it or not, I had to be around crowds for work. I still did fine though, didn't catch anything. I would say the most important thing is to wash hands often. Not just the patient but also everyone who's around them regularly. If you know someone is sick, stay away from them. I think everything will be fine if you do that. Best of luck to you and your wife. Hope she recovers and is cancer-free soon!

By fify — On May 02, 2012
My wife is about to start chemotherapy for breast cancer. Her doctor told us about the nadir period recently and being more careful to avoid any possible sources of infections during that time.

I've seen on some cancer support forums that nadir occurs about two weeks after starting chemotherapy. I'm sure that having the doctor check blood counts and give us more exact timing would be better. But is it okay to go by this information and take extra precaution around the second week mark after chemotherapy starts?

Is nadir pretty consistent in terms of timing for everyone or does it change from person to person?

And how careful do we need to be during the nadir period? My wife doesn't like being cooped up in the house but that's what I would like her to do if possible. I don't plan on letting her go to any crowded places, no shopping malls or restaurants during that time. Is that too extreme?

I would appreciate any suggestions on this if you or a close one has went through this as well. Thank you!

Mary McMahon

Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a...

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