I think every medical school should give its students an entire course just on energy. Reason: Conventional medical doctors are so focused on the diagnosis and treatment of disease that they are terrible at simply helping patients feel great.

A lack of energy can be a symptom of many different conditions. Some of the causes of fatigue have nothing to do with low energy — and they can be surprising to both patients and doctors. Here is information about the five hidden energy thieves that many doctors miss. Consider whether any of these situations might apply to you.

Chronic Infection

Samantha, a 45-year-old woman, was experiencing extreme fatigue after suffering a viral illness several months earlier. Blood tests did not reveal any lingering infection, though I had a hunch it was still there. To boost her immune system, I prescribed an antiviral regimen of high-dose vitamin C and immune-boosting herbs, such as astragalus and licorice. Within six weeks, she had completely recovered.

Recent research has shown that ongoing fatigue often is related to viral infections (such as Epstein-Barr or herpes) that never completely subside even though the virus can’t be detected by blood tests. When I take the medical history of a patient with fatigue, he or she frequently reports feeling unwell since suffering the flu or some other viral illness. What generally helps these patients fight off infection: High doses of vitamin C, sometimes delivered intravenously, and herbs (in addition to astragalus and licorice) such as lomatium, a liquid extract that strengthens the immune system.

The Digestion Connection

Jane, a 30-year-old illustrator, had been feeling tired for several months. She had a history of irritable bowel syndrome, a disorder of the intestinal tract. I had her begin a daily regimen of digestive enzymes and herbs (including gentian root and ginger) to improve her digestion. I also told her to avoid problem foods such as, in her case, dairy. Within two weeks, she felt better. After five months, she had completely regained her energy.

There’s a strong connection between your digestive system and your energy level. Even if you eat a healthful diet, you can have energy problems if your body can’t absorb the nutrients in the food that you’re eating. Improper digestion causes toxic metabolites to build up in your digestive tract. These particles migrate into the bloodstream and then to your body’s cells, where they disrupt normal function. When it is healthy, the small intestine acts as a barrier to bacteria and other toxins. But when it becomes inflamed because of an unhealthful diet or a digestive disorder such as irritable bowel or reflux, it does not absorb nutrients properly, resulting in a syndrome known as leaky gut. Both lack of nutrients and exposure to toxins can result in fatigue.

When digestion is back on track, energy improves. Supplements that can help: A full-spectrum digestive enzyme (available at health-food stores) that breaks down foods into usable nutrients can be taken with each meal. You also may be helped by gentian root and ginger, herbs that stimulate the body’s digestive juices… N-acetyl d-glucosamine (NAG), a sugar that reduces food sensitivity (500 mg three times daily)… and glutamine (1,000 mg three times daily before meals) or deglycyrrhizinated licorice (one 400-mg tablet three times daily before meals), both of which help heal the digestive tract and reduce inflammation.

Missing Nutrients

Bob, a 45-year-old nurse, had a five-year history of fatigue. A blood test revealed that he had low levels of a range of B vitamins. Within a week of receiving multiple B vitamins via intravenous therapy and a daily high-potency oral multivitamin, his symptoms improved significantly.

Deficiencies of vitamins and nutrients, such as B-12… magnesium… and/or the super antioxidant glutathione, all can contribute to fatigue. Unlike the digestion problems explained earlier, this type of nutrient deficiency is directly linked to not getting enough of a nutrient either because of poor diet, unhealthful lifestyle or aging. A blood test to determine which nutrients are low often is the best way to determine the cause of the problem — and then supplement accordingly.

When HGH is Imbalanced

Tony, a 64-year-old patient, had suffered from extreme fatigue for three years. He had telltale symptoms of human growth hormone (HGH) deficiency, including decreased muscle mass. Testing confirmed the deficiency, so I prescribed daily HGH injections. Within eight weeks, his fatigue was gone.

Hormone imbalances are a common, and often overlooked, cause of fatigue. HGH is one of the major hormones that, when deficient, can have a negative impact on energy. HGH peaks in the body during adolescence, then declines slowly with age. If levels drop too low, fatigue can result.

High HGH levels are associated with cancer risk, so people who are deficient and receive supplementation need to be monitored by a qualified physician. Those who are truly deficient, and receive treatment via injection, experience a boost in energy virtually overnight. After reaching optimum levels of the hormone, patients continue to sustain these levels with proper lifestyle and diet choices.

Other hormones that can become deficient and affect energy are those produced by the adrenal glands and the thyroid gland.

Blood Sugar Highs and Lows

Alice, a 38-year-old mother, had such severe fatigue that she couldn’t care for her children. If she waited longer than two hours between meals, her fatigue worsened. For me, that was the clue that her blood sugar might be low. An oral glucose tolerance test revealed that she had hypoglycemia (low blood sugar). I recommended a diet and supplement regimen to stabilize her blood sugar. Within a week of being on the program, Alice had her energy back.

Blood sugar that is either too low (as in hypoglycemia) or too high (as in untreated prediabetes or diabetes) can cause fatigue. In people with low blood sugar, there isn’t enough glucose in the blood to fuel the cells properly. In patients with prediabetes and diabetes, the body is less responsive to insulin, so sugar isn’t transported properly into the cells. Patients with high or low blood sugar need to balance amounts of healthful fats, carbohydrates and protein. Soluble fiber (found in foods like oatmeal and legumes) helps to slow the release of blood sugar.

Several supplements can help stabilize high or low blood glucose levels, including PGX, a soluble fiber supplement… alpha lipoic acid, an antioxidant that protects cells from damage… resveratrol, an antioxidant that reduces blood sugar… vitamin D-3… and blood sugar-balancing minerals (chromium and zinc) and herbs (gymnema sylvestre and bitter melon).

Now that you have a better understanding of the five hidden energy thieves, think about which, if any, of these circumstances apply to you. If they do, then take this article with you to your next doctor’s appointment and make a point of discussing it.