There are many possible causes of extreme tiredness in your legs, including a chronic infection (one in which you are running a constant low-grade fever), side effects from radiation and/or chemotherapy, chronic fatigue syndrome and related auto-immune conditions, multiple sclerosis and excess weight because of pregnancy or obesity. You may need to check all these out, but it might be helpful to first check whether your tiredness may be caused by restless legs syndrome.
Restless legs syndrome (RLS) may not sound to you like what you are experiencing. You may not know you are have RLS because is a sleep disorder. With RLS, when you are asleep, or in a truly relaxed waking state, your body still receives messages from your brain to move or jerk your legs. You may also feel unpleasant sensations of tingling, creeping, prickling or even painful feelings in your legs. But if you are asleep, you may not be aware of these sensation.
RLS has many triggers. Pregnancy, particularly in the last trimester, can trigger symptoms, though these usually disappear about a month after the baby is born. If you have anemia (low blood iron levels) it can trigger RLS. As the anemia is corrected, your RLS symptoms lessen. Chronic conditions such as diabetes, Parkinson's disease, kidney failure and peripheral neuropathy (the loss of feeling and/or numbness) in legs and feet may also contribute to RSL. Diet and environment also can contribute to RSL.
No tests exist for RLS. A proper diagnosis depends on your clear and comprehensive explanation of symptoms to your doctor. You may also want to go to a sleep disorder clinic. Failure to recognize and treat your RLS can affect your health, your job and your personal life.
Your doctor can prescribe medication to treat your RLS, once underlying disorders are ruled out. These can include ropinirole (Requip), clonazepan (Klonopin), Halcion, Valium and L-Dopa. L-Dopa (which enhances dopamine levels in the brain) is in bromocriptine (Parlodel) and pergolide (Permax). All these medications do have side effects, however, so you might want to start with diet, herbal supplements and behavioral changes, especially as concerns your sleep patterns.
Diet is key. Reduce your intake of caffeine, alcohol, sodium and sugar. If you are anemic, add folic acid, magnesium and iron supplements. Add vitamin E, and increase the amount of potassium-rich (bananas and avocados) and calcium-rich (broccoli, sardines and almonds) foods you eat. Herbal remedies also can help. Try chamomile and peppermint tea, St. John's Wort and melatonin. Gentle regular exercise, and relaxation techniques like yoga, Alexander Technique and biofeedback are good. Acupuncture also helps. A massage with essential oils like lavender, particularly before bedtime, will help you sleep.