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Safe Oxygen Levels: What Should Your Oxygen Level Be?

If you are using supplemental oxygen, it is important to understand what your oxygen levels should be and when your oxygen levels are not safe. Many people with COPD have oxygen levels that are below normal, even when using supplemental oxygen, so your normal oxygen saturation levels might be different from the norm.

So, what should your oxygen level be and at what point do your oxygen levels go from being below normal to unsafe?  Let’s first explore the difference between blood oxygen and oxygen saturation and what it means to have a low oxygen levels.

What is the Difference Between Blood Oxygen and Oxygen Saturation?

In order to fully understand what it means to have a low oxygen level, it is essential to understand the ways in which oxygen levels are measured. Blood oxygen measures both the oxygen content of the blood, along with the partial pressure of oxygen in the blood, which indicates whether the lungs are working as they should. Blood oxygen levels are measured using a test that pulls blood from an artery via an arterial blood gas (ABG) test. While the majority of blood tests are able to use blood taken from a vein, that blood has already passed through the tissues in the body and, during the process, oxygen is used up while carbon dioxide is produced. An ABG test requires blood from an artery because arterial blood provides accurate oxygen and carbon dioxide level measurements before the blood enters tissues in the body and the levels change.[1] Specifically, an ABG test measures the following:

  • Partial pressure of oxygen (PaO2): Measuring the pressure of oxygen that has been dissolved in the blood, along with how well oxygen is moving from the lungs into the blood, indicates whether your lungs are functioning properly.
  • Partial pressure of carbon dioxide (PaCO2): Similarly, measuring the pressure of carbon dioxide dissolved in the blood, along with how well carbon dioxide is moved out of the lungs from your blood, indicates how well your lungs are functioning.
  • pH of the blood: pH is measured via hydrogen ions in the blood. The pH of blood should be slightly basic, falling somewhere between 7.35 and 7.45.
  • Bicarbonate levels: Bicarbonate keeps the pH of the blood properly balanced, so incorrect bicarbonate levels may indicate the pH of the blood becoming too basic or acidic.
  • Oxygen content (O2CT) and oxygen saturation (O2 sats) values: Oxygen content literally measures the amount of oxygen inside the blood, while oxygen saturation measures how much of the blood’s hemoglobin is carrying oxygen.[1] 

Oxygen saturation measures the percentage of hemoglobin (Hgb) molecules that are carrying oxygen on specific binding sites, and each hemoglobin molecule can bind to four oxygen molecules when fully saturated.[2] Hemoglobin releases some of those oxygen molecules to the tissues when conditions are right, which is how our tissues become oxygenated. Measuring the amount of hemoglobin molecules that are saturated gives us the oxygen saturation percentage.[2] In comparison, an oxygen saturation measurement does not offer nearly as much information as a blood oxygen measurement. However, measuring a patient’s oxygen saturation is significantly easier. While getting a blood oxygen measurement requires taking blood from an artery—something that can only be done in a blood lab or in your doctor’s office—getting an oxygen saturation measurement simply requires putting a pulse oximeter on your fingertip. A pulse oximeter is a noninvasive tool that uses infrared and red light frequencies to determine the oxygen saturation percentage in your blood by measuring the light reflected off the oxygen molecules.[3] Using a pulse oximeter is painless and quick, making it the easiest way to check a patient’s oxygen levels.

Low Blood Oxygen Levels = Hypoxemia

Your blood oxygen level is the amount of oxygen circulating in your blood. When blood oxygen levels drop below normal, a condition known as hypoxemia occurs. In COPD, hypoxemia is a problem related to your breathing. Hypoxemia is determined by measuring the amount of oxygen present in a blood sample taken from an artery using an ABG test. Your oxygen saturation (sometimes called O sats or O2 sats) can also be estimated using a pulse oximeter, a small device that attaches to your finger and measures the oxygen saturation level in your blood.

The amount of gas in a system is defined by the amount of pressure exerted by that gas. This pressure is traditionally measured as height in millimeters (mm) of a column of mercury (Hg).[4] Normal arterial blood oxygen levels as measured by an arterial blood gas range from 75 to 100 millimeters of mercury (mm Hg), which is a measurement of the amount of oxygen that is dissolved in the arterial blood. According to the Mayo Clinic, values under 60 mm Hg usually indicate that a person needs supplemental oxygen. Normal oxygen saturation levels as measured by pulse oximetry range from 95% to 100%. Values under 90% are considered low.[5]  

Does that mean you should panic if you have an oxygen level 89? Not necessarily. And, now that you have a better understanding of this measurement system, what should your oxygen level be?

First you need to understand which level you are talking about: your blood oxygen level or your oxygen saturation. If you have a blood oxygen level between 100 mm Hg and 75 mm Hg, you are doing quite well! So that means that if this is the oxygen level you are speaking about, oxygen level 89, oxygen level 86 and oxygen level 80 would all be just fine. However, if you were actually talking about your oxygen saturation, a normal oxygen saturation level should fall between 95% and 100%; in this case, a measurement of 89% would be worrisome. 

Blood Oxygen Levels: What’s Unsafe?

Unsafe oxygen levels are determined by your doctor; however, you are considered to have a low oxygen level and qualify for supplemental oxygen by Medicare guidelines when your arterial blood gas is at or below 55 mm Hg and/or your pulse oximetry reading is at or below 88% under certain conditions. This does not mean that a pulse oximetry reading of 90% is safe for you, however. Whenever your oxygen levels drop for more than a short period of time, your organs and tissues do not get the oxygen they need to function properly. Over time, a low oxygen level can lead to serious health consequences, such as pulmonary hypertension (high blood pressure in the lungs) and polycythemia (increased amount of red blood cells).[6] 

As such, it is important to be aware of what your normal oxygen saturation and blood oxygen levels are. Ask your doctor to review a blood oxygen level chart with you so you know what your levels should be and when you should be concerned.

Maintaining Safe Oxygen Levels

safe oxygen levels

When you are given a prescription for supplemental oxygen, your doctor should give you a blood oxygen level chart and a safe range of oxygen saturation levels that they want you to maintain. You will likely need to have a pulse oximeter on hand so you can measure your oxygen saturation periodically. If you consistently fall below the normal oxygen saturation range your doctor has given you, even with your supplemental oxygen therapy, you should notify your doctor. It is likely an adjustment may need to be made in your oxygen flow rate or time used.

Your doctor may also give you permission to “titrate” your oxygen flow rate according to your oxygen saturation levels. For example, if your doctor determines that your safe oxygen saturation level should be 92% or above, they may advise you to increase your oxygen flow rate if your saturation drops below 92%. However, do not adjust your oxygen flow rate or the amount of time you use supplemental oxygen without getting express directions from your doctor. Maintaining safe and normal oxygen saturation levels is important for your health and well-being. If this becomes difficult for you, and you find you consistently have a low oxygen level even while on supplemental oxygen, talk to your doctor as soon as possible.

How to Maintain Safe Oxygen Levels Successfully

In order to avoid finding yourself with a low oxygen level, it is important that you know how to successfully maintain a safe oxygen level. This can vary from person to person, so always speak with your doctor first about the best ways to ensure your oxygen levels are as healthy as possible for you. That said, here are some general tips for checking and maintaining safe oxygen levels.

  • Check your pulse ox regularly. Keeping a pulse oximeter on hand is a great way to ensure that your oxygen levels are safe and healthy for you. Talk to your doctor about what you should do if you notice that your pulse ox measurement has dropped, and when to be concerned.
  • Keep a journal. This may not sound like much, but keeping a health journal can actually be extremely helpful for you and your health care team. Take note of any time your oxygen levels drop or times you experience symptoms of a low oxygen level, including headache, shortness of breath, dizziness, rapid breathing or heart rate and more. Similarly, take note of anything that seems to improve your oxygen levels or minimize your symptoms. It is likely that you will begin to see patterns in your activities and behaviors that impact the changes in your oxygen level.
  • Slow down a little. Sometimes, people begin to experience a low oxygen level because they are doing too much. It may be that your body simply requires a bit more rest from time to time.
  • Practice breathing exercises. There are a number of different breathing techniques, including pursed-lip breathing and diaphragmatic breathing, that can significantly improve your breathing and your oxygen levels.
  • Talk to your doctor about pulmonary rehabilitation. Pulmonary rehab can help you in a number of different ways, including helping you learn to breathe more efficiently, helping you improve your exercise tolerance, providing counseling, nutritional education and more.
  • Review your prescriptions. If you currently use oxygen therapy or medications to help you breathe better, find out if they may need to be adjusted. If you do not use these, it might be time to consider them. 

Frequently Asked Questions: Normal Oxygen Saturation

What should your oxygen level be when sleeping?

Normal oxygen saturation levels drop when we sleep because we breathe more slowly. Additionally, some of our alveoli are not used while we are asleep, which means our lungs are not as efficient. Typically, doctors prefer that your oxygen level stay at or above 90% while sleeping. If your normal oxygen saturation is above 94% while you are awake, your oxygen level is unlikely to fall below 88% while you sleep, but if your doctor is concerned, they may order an overnight pulse oximetry test to be sure. 

What level of oxygen is dangerous?

Only your doctor can determine what is dangerous for you, but there are some basic guidelines. Based on a standard blood oxygen level chart, an ABG measurement of 60 mm Hg or lower indicates the need for supplemental oxygen. A pulse oximeter reading under 90% is considered low and indicates the need for supplemental oxygen as well. 

Is an oxygen level 86 bad if I have COPD?

While people with COPD often have lower oxygen saturation and can safely fall between 92% and 88% when it comes to a normal oxygen saturation for them, it is still essential not to let it fall too low. An oxygen level below 88% can be dangerous for any period of time. An oxygen level below 85% warrants a trip to the hospital. Keep in mind that an oxygen level 80% and lower puts your vital organs in danger, so it is important to keep a blood oxygen level chart handy so you know what levels require immediate treatment. 

How do I test my oxygen levels at home? 

Checking your oxygen level at home is quite easy with a pulse oximeter. Simply attach your pulse oximeter to your pointer finger or middle finger so it is secure.[7] When the pulse oximeter is secure, it will not feel too tight or like it is restricting circulation, nor will it feel loose enough to fall off or move around and let other light in. When fitted properly on the finger, the lights from the pulse oximeter should be able to shine directly through your finger. Keep in mind that nail polish or other pigment (like a tattoo or henna), or even dirty fingernails, can interfere with a proper reading, so make sure your hands are clean and free of pigment when testing. While testing, make sure your device is fully charged and securely attached, then stay still and ensure that no bright lights are shining directly on the pulse oximeter during the measurement.[8] If you are unsure whether you are using your pulse oximeter correctly, ask someone on your health care team to help guide you through the process. 


[1] “Arterial Blood Gases.” Michigan Medicine, University of Michigan, 9 June 2019, www.uofmhealth.org/health-library/hw2343.

[2] Whitten, Christine. “What’s The Difference Between Oxygen Saturation And PaO2?” The Airway Jedi, The Airway Jedi, 22 Sept. 2019, airwayjedi.com/2015/12/09/difference-oxygen-saturation-pao2/.

[3] Fahy, Bonnie, et al. “Pulse Oximetry.” American Thoracic Society, Mar. 2018, https://www.thoracic.org/patients/patient-resources/resources/pulse-oximetry.pdf.

[4] Higgins, Chris. “Why Measure Blood Gases? A Three-Part Introduction for the Novice – Part 1.” Acute Care Testing, Radiometer Medical, Jan. 2012, acutecaretesting.org/en/articles/why-measure-blood-gases-a-three-part-introduction-for-the-novice-part-1.

[5] “Hypoxemia (Low Blood Oxygen).” Mayo Clinic, Mayo Foundation for Medical Education and Research, 1 Dec. 2018, www.mayoclinic.org/symptoms/hypoxemia/basics/definition/sym-20050930.

[6] Kent, Brian D, et al. “Hypoxemia in Patients with COPD: Cause, Effects, and Disease Progression: COPD.” International Journal of Chronic Obstructive Pulmonary Disease, Dove Press, 14 Mar. 2011, doi.org/10.2147/COPD.S10611.

[7] Basaranoglu, Gokcen, et al. “Comparison of SpO2 Values from Different Fingers of the Hands.” SpringerPlus, Springer International Publishing, 29 Sept. 2015, www.ncbi.nlm.nih.gov/pmc/articles/PMC4627972/.

[8] “Using the Pulse Oximeter.” World Health Organization, 2011, https://www.who.int/patientsafety/safesurgery/pulse_oximetry/who_ps_pulse_oxymetry_tutorial2_advanced_en.pdf?ua=1.

Additional Sources 

Katsenos, Stamatis, and Stavros H Constantopoulos. “Long-Term Oxygen Therapy in COPD: Factors Affecting and Ways of Improving Patient Compliance.” Pulmonary Medicine, U.S. National Library of Medicine, 15 Sept. 2011, pubmed.ncbi.nlm.nih.gov/21941649/.

Leader, Deborah. “Understanding Oxygen Saturation.” Verywell Health, Verywell Health, 7 May 2020, www.verywellhealth.com/oxygen-saturation-914796.

“The Need For Supplemental Oxygen.” UCSF Health, UCSF Health, 31 Oct. 2019, www.ucsfhealth.org/education/supplemental_oxygen/the_need_for_supplemental_oxygen/.

“Oxygen Saturation (Medicine).” Wikipedia, Wikimedia Foundation, 19 May 2020, en.wikipedia.org/wiki/Oxygen_saturation_(medicine).

Silva, Joana Cavaco. “Normal Blood Oxygen Levels: What Is Safe and What Is Low?” Medical News Today, MediLexicon International, 28 Jan. 2020, www.medicalnewstoday.com/articles/321044.php.



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