If you are always tired you may have already told your doctor about the problem, only to hear him/her say: “According to your lab tests, there isn’t anything wrong with you”, or “I have good news, your tests are normal, you are just fine”.

Well, if this is the case and you are on prescription drugs such as diuretics, consider the possibility that the drugs you are taking may be the reason why you are always tired since one of many side effects of many commonly used prescriptions and non-prescription drugs is fatigue.

Many prescription drugs can make you tired directly or indirectly; some can make you extremely fatigued, some may cause only minor fatigue. Some drugs that can rob your energy include:

  1. Anti-hypertensives
  2. Antidepressants
  3. Tranquilizers
  4. Sleeping pills
  5. Antihistamines
  6. Antibiotics
  7. Diuretics
  8. Illicit drugs
  9. Alcohol

Some prescription drugs may lead to nutrient deficiencies

One way prescription drugs may cause you being always tired is by depleting your body of nutrients. Here is how it can happen:

Diuretics cause loss of potassium and magnesium, which can lead to fatigue.
Dilantin can cause deficiency of folic acid, which we know it can cause fatigue.
Chronic use of aspirin can lead to loss of folic acid and iron.
The high blood pressure medication, hydralazine, is a vitamin B6 antagonist, meaning they don’t get along which causes a loss of this vitamin.
Use of cimetidine (Tagamet) to treat ulcers can lead to deficiency of B12.
Some drugs, such as tricyclic antidepressants may cause loss of appetite.
Other medications can cause malabsorption which means your body does not get the nutrients it needs and can make you very tired.

Prescription drugs can add a toxic burden to your body

Prescription drugs can also contribute to make you toxic and interfere with the elimination mechanisms of your body. Some drugs affect the liver’s ability to detoxify foreign chemicals by blocking an enzyme system known as the “Mixed function oxidase system”. By blocking the liver’s detoxifying mechanisms, you are exposed to environmental chemicals which in turn can also produce fatigue.

Some types of headaches, such as chronic tension-type headaches, have been related to toxicity symptoms. Pain relievers such as aspirin or acetaminophen, even in small quantities as ten tablets per week, have been found to cause chronic headaches because they interfere with the liver’s normal detoxication mechanisms.

Coloring and additives in prescription drugs

Drugs may also contribute to your symptoms of fatigue because they contain coloring, additives and preservatives to which you may be sensitive. Many drugs for example contain sulfites, which may adversely affect asthmatics. Food colorings such as #5 and yellow #6 are widely used in the manufacture of drugs and cause adverse reactions in certain hypersensitive patients.

Is your doctor informing you?

Many doctors are not aware of the interaction between food and the drugs they prescribed. For this reason, you may have to do your homework or consult with a nutrition-oriented doctor.

If your doctor does not adequately address the issue, look up the name of your medication in a Physician’s Desk Reference at your public library and check if fatigue is listed as a complication or you can go to the Physician ’s Desk Reference

Quite often, fatigue is not listed as a symptom if it has not occurred in a high percentage of people. However, it may still affect you. Talk with your pharmacist and ask if the medication you are on can cause fatigue as a side effect.

If your pharmacist answers “yes”, ask which other medication might serve the same purpose without inducing fatigue. Only your doctor can make the change in prescription, the pharmacist cannot do this, but you will have the information you need to go to your doctor.

Laboratory tests to detect some causes of fatigue

There are no standard laboratory tests to determine if medication is causing your fatigue. Your test is whether your fatigue symptoms improve after changing or discontinuing the drug. However, since many drugs affect your levels of vitamins and minerals, you may suggest to your doctor to order a lab test to assess the nutrition status of some of them.

Blood Test

Each of us produces energy from our food in very predictable ways. The basic biochemistry is reasonably well understood. When someone suffers from fatigue it often means that something is not working in the production of energy. It seems reasonable that to assess this malfunction, we run tests that look at the different energy pathways and the nutrients that may be missing to carry out the necessary functions.

You need to obtain the right tests

You may have gone to your doctor with a fatigue problem, only to have your doctor say: According to your lab tests, there isn’t anything wrong with you”, or “I have good news, your tests are normal, you are just fine”. What is happening here: you don’t feel well but your tests are fine?

The answer may lie in the fact that:

Many of the commonly tests ordered are only altered when disease or pathology exists.
Second, the doctor must order the right test to determine what’s wrong.

By ordering the usual lab test, called a SMAC, your doctor may be missing the fact that you may have a deficiency of nutrients such as magnesium, tryptophan, taurine, tyrosine, B1, B6 and B12. They are not part of this usual lab test.

Most appropriate tests to detect fatigue

Amino acid analysis (blood or urine). When you eat chicken, beef, eggs, beans, etc., the protein is broken into a series of smaller molecules called amino acids, the building blocks of protein in the body. Amino acids are needed to form new proteins, enzymes, hormones, neurotransmitters and many other molecules.

If the metabolism of amino acids does not work properly and certain amino acids are missing, then the production of energy and the functions of the heart, brain, muscles and many other are not carried out properly, leading to fatigue.

All these functions are also dependent on adequate vitamins and minerals. If an amino acid, a key vitamin, or a key mineral is not present in sufficient amounts, the production of energy in the body can be disrupted. An amino acid analysis gives your doctor a good base to determine your health status.

Functional vitamin tests

Most standard blood tests for vitamins do not take into consideration that there are other body substances or fluids that store vitamins. B12 is a good example. Many cases have been reported of normal blood B12 yet the patient improved on B12 supplements.

Some tests presently available for vitamins include the following:

Thiamin (B1): Erythrocyte transketolase (ETK)
Riboflavin (B2): Glutathione reductase (GSR)
Cobalamin (B12): Methylmalonic acid, amino acid analysis
Niacin (B3): 1-N-methylnicotinamide
Folic acid: Homocysteine, formiminoglutamic acid
Pyridoxine (B6): amino acid analysis, erythrocyte glutamate oxaloacetate transaminase (EGOT)
Vitamin C: white blood cell ascorbate

Organic acid analysis

“Organic acids” is a term used to describe a large number of compounds derived from protein, fat, and carbohydrate and they are very important in the production of energy. For example, the Krebs cycle (or citric acid cycle) is one of the most important energy pathways in the body. This type of analysis can shed light on where the energy production might be blocked and gives insight into which vitamins, minerals, or amino acids might be needed therapeutically. Organic acid analysis is performed on urine.

EMA Nutrient Analysis

This test, called “Essential Metabolics Analysis” measures the way different vitamins and minerals affect the growth of white blood cells called lymphocytes, the cells of the immune system. It measures the status of:

  1. Vitamins B1, B2, B3, B6, B12, folic acid, pantothenic acid and biotin
  2. Minerals: calcium, magnesium, zinc
  3. Amino acids: glutamine, asparagine, serine
  4. Fatty acids: oleic acid
  5. Carbohydrates: glucose/insulin metabolism, fructose intolerance
  6. Metabolites: choline, inositol

The bottom line

As you can see here, it is better not to take vitamins and supplements on your own without talking to your doctor. However, if you feel very tired and your doctor keeps telling you everything is fine with you, you may ask your doctor to order some of these tests to have a better knowledge of your health statue. He/she may find out that you need therapeutical doses of some vitamins and prescribe them.


I am Andy Carpenter and I would start by saying that I have a Bachelor Degree in Nutrition Science conferred by California State University, Los Angeles and that I am certified as a Registered Dietitian.

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