The previous chapter discussed the link between physical and mental illness. Here, we’ll describe tests for common problems affecting mental health. No, there is not a blood test to diagnose mental illness. But when you first talk to a doctor, don’t be surprised if they reach for a lab requisition form rather than a prescription pad.
We don’t recommend you be tested for everything imaginable. That would be a spectacular waste of resources. At the same time, you shouldn’t be left unable to function for years because someone didn’t order an inexpensive blood test. One of the best ways to avoid unnecessary testing is knowing what’s already been tested. If you have a regular family doctor, your lab results are probably in their Electronic Medical Record (EMR) system. But, that doesn’t mean that other doctors know about them.1
Most family doctors send recent lab test results to specialists when you are referred, but not always. They may also neglect to send tests done later. If you’ve had recent tests, make sure everyone involved in your care knows about it. The best way is to get copies of your own results. You may be able to see your results online or ask the lab or your doctor for a copy. This also helps if you see multiple doctors. It can save a lot of hassle, money, and time.
Low iron can cause several symptoms also found in those with depression. These include fatigue, decreased energy, memory problems, and poor concentration. It can cause restless legs often thought to be solely due to medication. Low iron can also affect your treatment. It reduces the effectiveness of psychotropic medications, limits your exercise capacity, and more.
Routine blood work will check your hemoglobin, the iron-rich component of your blood. That test detects only very low iron. However, even a moderate deficiency can impact mental health. A better measure is serum ferritin (stored iron). Labs consider normal ferritin to be about 15–270 µg/l. However, if you have mental health concerns, 15 is too low. It should be higher, preferably at least 50.
We’ve seen many people whose “depression” disappears after treating their iron deficiency. This is one of the few no-brainer fixes. Also, keep in mind that your iron levels can change over time. Has your energy decreased or your concentration worsened, for no apparent reason? Has a long-term medication become less effective or “pooped out” altogether? Ask your doctor to recheck your ferritin before making other changes.
The test for serum ferritin indicates how much iron is stored in your blood outside your red blood cells. A routine complete blood count (CBC) measures hemoglobin, the iron inside your red blood cells. You can have normal hemoglobin but low ferritin.
Iron stores help with many things, including building neurotransmitters. Too little iron means too few neurotransmitters. Trying to fix depressive symptoms brought on by low iron with treatments such as antidepressants won’t work. Low iron can impair energy, concentration, and memory.
Low iron may mean you don’t get enough in your diet, you may absorb it poorly, or you may have heavy bleeding or another illness. Changes in diet, supplements, or working with your doctor to deal with physical illnesses can help.
If iron deficiency is the number one missed opportunity for a quick fix, low vitamin B12 runs a close second. Like iron, B12 is needed to make red blood cells, as well as for the proper operation of the nervous system. A severe deficiency can cause similar problems: weakness, fatigue, numbness, tremor, depression, anxiety, confusion, and poor memory.
Low B12 can result from inadequate dietary intake. As B12 is not naturally found in plant foods, vegans require fortified foods or supplements. Absorption problems can also reduce B12 levels. The ability to absorb vitamin B12 decreases with age, so this affects seniors more frequently. Many of the cognitive symptoms of B12 deficiency mimic those of early-stage dementia. A missed blood test can result in unnecessary concern.
Again, the normal reference range for vitamin B12 is a bit too low, typically around 150–655 pmol/l. Studies have shown that for those experiencing mental health symptoms, the minimum level should be higher—at least 240 pmol/l. A vitamin B12 deficiency can be easily missed. For those with very low B12, recovery after starting oral supplements or a quick injection can be dramatic.
Like iron, B12 is needed to create neurotransmitters such as serotonin, norepinephrine, dopamine, and GABA. It also serves another important function in the nervous system, producing myelin. Myelin is an insulating layer that surrounds the long axons of nerves, acting like insulation around an electrical wire. A lack of myelin reduces the ability of nerves to send signals. This leads to a variety of mental health and neurological problems.
Many other vitamins and minerals are needed for mental well-being. They are needed to create neurotransmitters, regulate levels of neurotransmitters or hormones, and keep neurons working. These include other B vitamins such as B6 and B9 (folate), vitamin C, vitamin D, zinc, selenium, iodine, chromium, and electrolytes (sodium, potassium, calcium, and magnesium).
It would be overkill to initially test all of these purely for mental health reasons. Iron and B12 deficiencies are far more common causes of mental health symptoms. Many deficiencies are rare, especially with the number of foods being fortified with essential nutrients. After you’ve tried several treatments without success, testing for less common deficiencies may be warranted. You may have done the basic tests, tried a few medications, verified your diagnosis, and ruled out causes that won’t respond to medications. That’s the time to start considering more obscure causes.
Cost is also a factor. Consider vitamin D. Research in the early 2000s linked low vitamin D with various physical and mental illnesses. As a result, testing rates spiked at least 5–10 times in a few years. Testing among US Medicare beneficiaries increased 83 times. That cost adds up quickly.
Your body makes vitamin D when your skin is exposed to direct sunlight. Most people in northern countries such as Canada, where the sun is at a low angle much of the year, are probably deficient. However, five years’ worth of a generic vitamin D supplement can cost less than a single test. It makes more financial sense to have everyone take a supplement and not test. Testing is therefore often not covered by insurance.
Still, many people are hesitant to take a supplement based on the assumption they’re probably deficient. Showing them their actual vitamin D level may be enough to convince them to take it.
Hormones are chemical messengers that regulate and control a wide range of body systems, including your mood. Your thyroid hormones are frequently checked by doctors when investigating mental health symptoms. The thyroid is a gland in your neck that makes hormones to regulate metabolism. An underactive thyroid can leave you fatigued, moody, or depressed. An overactive thyroid causes anxiety, irritability, and insomnia.
Blood tests can directly measure the thyroid hormones (T3 and T4). More often, a thyroid stimulating hormone (TSH) produced by the pituitary gland is measured instead. It’s a more sensitive measure of thyroid problems. When you have symptoms of depression such as fatigue, your doctor is more likely to check your TSH than just prescribe an antidepressant.
While TSH is the only hormone routinely checked for mental health purposes, others may be checked in certain special cases. These include various sex hormones, including testosterone, estrogen, progesterone, and prolactin, as well as stress hormones including adrenaline, cortisol, and DHEA. And, of course, all these various hormones and neurotransmitters interact with one another. A problem with one is likely to cause ripple effects.
Before prescribing any medications, your doctor may want to check your liver and kidneys, depending on your overall health.
Your liver metabolizes most medications, breaking them down into a form that can be directly used or into waste materials that can be removed. If your liver isn’t working well, many medications won’t work. Liver function tests (LFTs) measure levels of certain enzymes, e.g., ALT and AST.
Your kidneys filter out waste materials including many medications. If not working well, medications may build up to toxic levels. The most common test measures creatinine, a waste product from your muscles. Too much creatinine is a sign your kidneys aren’t removing it well.
Other tests may help decide whether to use certain medications. As an example, some medications are more likely than others to increase cholesterol or blood glucose when taken for a long time. If your levels are already high, your doctor may want to monitor them more often if you do take the medication or decide to use a different medication altogether.
Some of your symptoms, mental health or otherwise, may cause your doctor to consider the possibility of another physical illness. If so, they may order other tests specifically for that condition.
Beyond common blood tests, your doctor may order other tests.
The most routine is an electrocardiogram (ECG or EKG). This is a tracing of your heart’s electrical activity recorded by multiple leads attached to your body. ECGs detect many structural or functional abnormalities in your heart such as a previous heart attack. Like testing cholesterol or glucose, an ECG helps your doctor decide how safe it is to use certain medications.
Certain older medications can worsen some heart problems. Alone or in combination, they can raise or lower your blood pressure, heart rate, or other measures that could magnify a borderline heart condition. A baseline ECG before you start a medication, or a check afterwards is a simple precaution that can prevent a very rare but serious outcome.2
One such measure is your QT interval, which is the length of time between two specific points in your heart rhythm. If it is much longer than normal, called QT prolongation, it puts you at risk of potentially dangerous heart rhythms. Many medications, including psychotropic medications (but also many antibiotics, antihistamines, gastrointestinal medications, cancer medications, and others) can increase the QT interval. It’s rarely a problem unless it starts out very high (it can be inherited) or you take several medications that increase it. Tell your doctor about all your medications and supplements. Mention any heart problems you or any close relatives have.
Some symptoms may prompt your doctor to request a picture of your brain to look for any physical problems. This is not only to look for brain tumours but also various structural issues. Standard tests include a computed tomography (CT) or magnetic resonance imaging (MRI) scan. If something is out of whack with your hormones, they may even order scans for other parts of your body, such as your adrenal glands, which sit atop your kidneys.
While both CT and MRI scans of the brain are useful, each has advantages and disadvantages. CT, which use X-rays, may be faster or cheaper. CT is often the only option for very heavy patients or those who are claustrophobic. While MRI cannot be used safely if you have implanted metal of some kind, CT can be used. Either one can detect a wide range of problems, including bleeding and tumours, and both produce detailed images. MRI uses magnets and radio waves, so there is no concern of radiation exposure. MRI can more easily visualize some areas, such as the back of the brain, that CT cannot. MRI can pick up many differences in soft tissues, such as changes in the brain’s white matter, that aren’t visible with CT. The choice of which test to use will depend on what your doctor is looking for.
Newer imaging techniques include PET and SPECT scans. They show how different areas of the brain function, displaying higher or lower activity. Characteristic changes have been seen for several mental illnesses. While used mostly in larger centres now, expect their use to grow in future.
Another test is an electroencephalogram (EEG), which checks the electrical activity in the brain. Like an ECG, electrical leads are attached, this time to your head, and your brain waves are recorded. It’s not a common test for mental health purposes. However, a few mental health symptoms, e.g., smelling things that aren’t there, can be caused by certain seizure disorders, which an EEG can pick up.
Lab investigations can detect many problems that contribute to mental health symptoms. Some vitamins and minerals are needed, directly or indirectly, to create neurotransmitters or help with their transmission.
Iron deficiency is a very common cause of symptoms such as poor energy, concentration, and memory. There are many different ways to measure iron but, for mental health, serum ferritin should be evaluated. You will also need amounts higher than the normal ranges indicated on lab reports.
Vitamin B12 deficiency also affects mental health symptoms. Other common tests include those for your thyroid (TSH), liver, and kidneys.
An electrocardiogram (heart tracing) can check for rare but serious problems. Other tests can include imaging the structure of your brain (CT or MRI), its electrical activity (EEG), or its metabolism (PET or SPECT).
If and how lab results are shared varies by jurisdiction and organization. Some of the variation is due to logistics (e.g., hooking everything up), maintenance costs, and privacy concerns. and who is going to pay to maintain that service. Some of this is concerns over privacy rights. For example, in Alberta, there is a central database called NetCare for all lab results. It lets doctors look up results online. The catch is that not every doctor can use NetCare (especially those in smaller offices), due to very rigid privacy safeguards.↩
Practice guidelines can be either vague (“for high-risk patients”) or altogether silent around who should be screened or monitored. A group in the Netherlands recently proposed a pragmatic set of criteria as a starting point to help fill this gap.
Simoons M, Seldenrijk A, Mulder H, Birkenhager T, et al. “Limited Evidence for Risk Factors for Proarrthymia and Sudden Cardiac Death in Patients Using Antidepressants: Dutch Consensus on ECG Monitoring.” Drug Safety. 2018;41(7):655-664.
https://doi.org/10.1007/s40264-018-0649-z↩
Now Available! A MSP-supported live course for BC residents based on the book. [Mar/2023]
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Now Available! A MSP-supported live course for BC residents based on the book.
