6 Commonly Used Blood Tests for Older Adults
In this article, We’ll address a real mainstay of modern medicine: laboratory tests that require drawing blood.
This is sometimes referred to as “checking labs,” “doing bloodwork,” or even “checking blood.” Most older adults have been through this. For instance, it’s pretty much impossible to be hospitalized without having bloodwork done, and it’s part of most emergency room care. Such testing is also often done as part of an annual exam, or “complete physical.” Last but not least, blood testing is usually — although not always — very helpful when it comes to evaluating many common complaints that affect aging adults.
Fatigued and experiencing low energy? We should perhaps check for anemia and thyroid problems, among other things.
Confused and delirious? Bloodwork can help us check on an older person’s electrolytes (they can be thrown off by a medication side-effect, as well as by other causes). Blood tests can also provide us with information related to infection, kidney function, and much more. Like much of medical care, blood testing is probably overused. But often, it’s an appropriate and an important part of evaluating an older person’s health care concerns. So as a geriatrician, I routinely order or recommend blood tests for older adults.
Here are six types of tests that we often order on our older patients:
1. Tests related to thyroid function
What these measure: These tests can be used to screen for thyroid disorders, or to help calibrate the dosage of thyroid replacement medications. The most commonly used tests are:
In more complicated situations, other tests related to thyroid function may also be ordered.
What these tests are often used for:
- Thyroid problems are common in older adults (especially older women), and are associated with symptoms such as fatigue and cognitive difficulties.
- If an older person is having symptoms that could be related to a thyroid problem, the first step is to check the TSH level.
- TSH usually reflects the body’s determination of whether the available thyroid hormone is sufficient or not.
- If the thyroid gland is not making enough thyroid hormone, TSH should be higher than normal.
- Free T4 is often used to confirm a thyroid hormone problem, if the TSH is abnormal.
For more information about thyroid problems in older adults, see HealthinAging.org: Thyroid Problems. You can also read a more in-depth scholarly article here: Approach to and Treatment of Thyroid Disorders in the Elderly.
2. Tests related to vitamin B12 levels
What these measure: These measure the serum levels of vitamin B12 and provide information as to whether the level is adequate for the body’s needs. The two tests involved are:
Depending on the situation, if an older adult is found to have low vitamin B12 levels, additional testing may be pursued, to determine the underlying cause of this vitamin deficiency.
What these tests are often used for:
- Vitamin B12 deficiency is quite common in older adults, and can be related to common problems such as fatigue, memory problems, and walking difficulties.
- Methylmalonic acid levels in the body are related to vitamin B12 levels, and can help confirm a vitamin B12 deficiency.
- It is especially important to check this, if an older person has vitamin B12 levels that are on the low side of normal.
- Low vitamin B12 levels are associated with higher-than-normal methylmalonic acid levels
- For more information, see: How to Avoid Harm from Vitamin B12 Deficiency.
3. Glycated hemoglobin (Hemoglobin A1C)
What it measures: Glycated hemoglobin is formed in the body when blood glucose (blood sugar) attaches to the hemoglobin in red blood cells. It is normal for glucose to do this, but if you have more glucose in the blood than normal, your percentage of glycated hemoglobin will be higher than normal. The higher one’s average blood sugar level, the greater percentage of glycated hemoglobin one will have. A result of 6.5% or above is suggestive of diabetes. For more information:
What this test is usually used for:
- This test is most often ordered to monitor the blood sugar control of people with diabetes.
- Whereas a blood glucose level (which can be checked by fingerstick or as part of a basic metabolic panel) reports the blood glucose level at a specific moment in time, a hemoglobin A1C reflects how high a person’s blood sugar has been, on average, over the prior three months.
- A hemoglobin A1C test can also be used as part of an evaluation for possible diabetes or pre-diabetes.
- Older adults should work with their doctors to determine what A1C goal is right for them. It is often appropriate to aim for a slightly higher goal in older adults than in younger adults. For more on this, see HealthinAging.org: Diabetes Care & Treatment.
4. Prothrombin time (PT) and International Normalized Ratio (INR)
What it measures: These two tests are used as a measure of how quickly a person’s blood clots. People taking the blood-thinner warfarin (brand name Coumadin) must have this regularly monitored. For more information:
What this test is usually used for:
- The INR is calculated by the laboratory, based on the prothrombin time. In people taking warfarin, the usual goal is for the INR to be between 2.0 and 3.0.
- The most common reason older adults take warfarin is to prevent strokes related to atrial fibrillation.
- Warfarin may also be prescribed after a person has experienced a blood clot in the legs, lungs, or elsewhere.
- The prothrombin time is also sometimes checked if there are concerns about unexplained bleeding, severe infection, or the ability of the liver to synthesize clotting factors.
5. Brain natriuretic peptide (BNP) test
What it measures: Despite the name, BNP levels are mainly checked because they relate to heart function (not brain function!). BNP levels go up when a person’s heart cannot pump blood as effectively as it should, a problem known as “heart failure.” For more information on this test:
A related, but less commonly used, test is the “N-terminal pro-B-type natriuretic peptide” (NT-proBNP) test.
What this test is used for:
- Checking a BNP level is mainly used to evaluate for new or worsening heart failure. This is a common chronic condition among older adults, which can occasionally get worse.
- The BNP test can be especially useful in evaluating a person who is complaining of shortness of breath.
- Shortness of breath can be caused by several different problems, including pneumonia, chronic obstructive pulmonary disease, pulmonary edema, angina, and much more.
- A low BNP level means that at that moment, the shortness of breath is unlikely to be due to heart failure.
- Checking BNP levels over time is also sometimes used to monitor a person’s heart failure and response to treatment.
- For more about heart failure, see MayoClinic.org: Heart failure tests and diagnosis and also HealthinAging.org: Heart failure.
6. Ferritin
What it measures: The body’s serum ferritin level is related to iron stores in the body. For more about this test:
Depending on the situation, if an older person’s iron levels need further evaluation, additional tests can be ordered.
What this test is used for:
- Ferritin levels are most commonly used as part of an evaluation for anemia (low red blood cell count). A low ferritin level is suggestive of iron-deficiency, which is a common cause of anemia.
- Studies estimate that only a third of anemias in older adults are due to deficiencies in iron or other essential elements.
- It’s important to confirm iron deficiency by checking ferritin or other tests, before relying on iron to treat an older person’s anemia.
- Ferritin levels are also influenced by inflammation, which tends to make ferritin levels rise.
- If the ferritin levels are borderline, or if there are other reasons to be concerned about an older person’s ability to manage iron, additional blood tests related to iron may be ordered.
- For more on evaluating and treating anemia in older adults, see Anemia in the Older Adult: 10 Common Causes & What to Ask.
Obviously, there are many more tests that can be ordered as part of the medical care of older adults. But the tests I cover above are, by far, the ones I order the most often.
