Get­ting plenty of sleep but still exhausted? Before you blame your multi-tasking, super-woman lifestyle, learn more about what might be at the root of your unex­plained fatigue.

We are in the midst of a global energy cri­sis but it has noth­ing to do with oil. The prob­lem is unex­plained fatigue.

“I’m so tired; I just can’t do what I used to do.”

“I’d love to go but hon­estly, I just don’t have the energy.”

“Sex? You mean right now?”

If you’re like most women, these phrases have become mantras, the echo of our col­lec­tive yawn grow­ing louder every day.

“The sin­gle biggest com­plaint I hear from my patients, day in and day out, is fatigue,” says car­di­ol­o­gist Nieca Gold­berg, MD, Direc­tor of the NYU Med­ical Cen­ter Women’s Heart Pro­gram and asso­ciate pro­fes­sor at the NYU School of Medicine.

Of course, for some of us the prob­lem is sim­ply multi-tasking to the max and not get­ting enough sleep, or good qual­ity sleep. “If you’re con­tin­u­ally log­ging in just 5 or 6 hours a night, it’s going to catch up with you, no mat­ter your age,” says Rebecca Amaru, MD, clin­i­cal instruc­tor of obstet­rics and gyne­col­ogy at the Mount Sinai Med­ical Cen­ter in New York City.

But if you are get­ting a healthy 7 to 8 hours a night and you’re still tired, Gold­berg says it’s time for a check-up to uncover the causes for fatigue.

“If your fatigue goes on for more than a week and there is no expla­na­tion for feel­ing tired, then yes, see your doc­tor,” says Goldberg.

While occa­sion­ally fatigue may be a sign of a seri­ous ill­ness, experts say most often it’s caused by a minor prob­lem, with a rel­a­tively easy fix.

To help you zero in on why you can’t stop yawn­ing, here are 7 hid­den causes of fatigue — poten­tial health prob­lems you should dis­cuss with your doctor.

Fatigue Cause # 1: Anemia

“If you are in your repro­duc­tive years, and par­tic­u­larly if you expe­ri­ence heavy men­strual cycles, have fibroid tumors or uter­ine polyps, or if you’ve recently given birth, the blood loss may have caused you to develop ane­mia — a lead­ing cause of fatigue in women,” says Amaru.

Prob­lems occur, she says, when the bleed­ing leads to a defi­ciency of hemo­glo­bin, the iron-rich pro­tein in red blood cells that car­ries oxy­gen from the lungs to other parts of your body. When your tis­sues and organs don’t get enough oxy­gen, she says, the result is fatigue.

Other causes of ane­mia include inter­nal bleed­ing, or a defi­ciency of iron, folic acid, or vit­a­min B12. Ane­mia may also be caused by chronic dis­eases like kid­ney dis­ease, for exam­ple. Symp­toms can include dizzi­ness, feel­ing cold, and irritability.

To con­firm a diag­no­sis of ane­mia, your physi­cian will give you a blood test. Treat­ment, she says, usu­ally con­sists of iron sup­ple­ments if iron defi­ciency is the cause, and adding iron-rich foods — such as spinach, broc­coli, and red meat — to your diet.

The good news: With effec­tive treat­ment, your fatigue should begin to lift in thirty days or less.

Fatigue Cause # 2: Under­ac­tive thy­roid (hypothyroidism)

If you are gen­er­ally slug­gish, run down, and even a lit­tle depressed, Gold­berg says the prob­lem may be a slow thy­roid, also known as hypothy­roidism. The thy­roid is a small, but­ter­fly shaped gland that sits at the base of your neck and con­trols your metab­o­lism, the speed at which your body operates.

“I believe that undi­ag­nosed thy­roid dis­or­der is one of the major female health prob­lems in this coun­try. I think it is even more wide­spread than any­one real­izes,” says Goldberg.

Accord­ing to the Amer­i­can Thy­roid Foun­da­tion, by age 60 approx­i­mately 17% of all women will have a thy­roid dis­or­der and most won’t know it. The most com­mon cause, they say, is an autoim­mune dis­or­der known as Hashimoto’s thy­roidi­tis. This con­di­tion causes the body to destroy the cells respon­si­ble for pro­duc­ing thy­roxin and other hor­mones secreted by the thy­roid gland. The result is hypothy­roidism, or a slow metabolism.

Blood tests known as T3 and T4 will detect thy­roid hor­mones. If these hor­mones are low, Gold­berg says syn­thetic hor­mones can bring you up to speed and you should begin to feel bet­ter fairly rapidly.

Fatigue Cause # 3: Undi­ag­nosed Uri­nary Tract Infec­tion (UTI)

Although most women asso­ciate a uri­nary tract infec­tion with symp­toms such as burn­ing or urgency, Gold­berg says in some instances fatigue may be your only clue.

“Not every woman has obvi­ous symp­toms of a UTI. Some have no symp­toms or mild symp­toms that go unno­ticed, except for the fatigue,” she says.

In most instances, a UTI is caused by bac­te­ria in the uri­nary tract, often the result of improper bath­room hygiene (wip­ing back to front, for exam­ple). Sex­ual inter­course can increase the risk because it can push bac­te­ria from the vagina into the urethra.

If your physi­cian sus­pects that you have a UTI, your urine will be tested. Treat­ment is quick and easy, and usu­ally involves an oral antibi­otic med­ica­tion. Gold­berg says the fatigue will lift within a week or less.

If your symp­toms return, get tested again, she says, because in some women, UTI’s are chronic. If this is the case, talk to your doc­tor about pre­ven­tive care, includ­ing low dose antibiotics.

Fatigue Cause # 4: Caf­feine Overload

Many of us grab a cof­fee or cola for a quick burst of energy, but for some women, caf­feine can have the oppo­site effect.

In an arti­cle pub­lished in the jour­nal US Phar­ma­cist, author W. Stephen Pray, PhD, RPh, reports that caf­feine is a stim­u­lant, but if you take too much, the tables can turn.

“In some patients, con­tin­ued abuse results in fatigue,” accord­ing to Pray. And if you think this means you sim­ply require more caf­feine to get the kick, this isn’t the case. “Any attempts to solve the prob­lem by increas­ing caf­feine intake causes the fatigue to worsen,” he says.

The solu­tion: Elim­i­nate as much caf­feine from your diet as pos­si­ble. This means not only cut­ting out cof­fee. Choco­late, tea, soda and even some med­ica­tions also con­tain caf­feine and could be caus­ing unex­plained fatigue.

Fatigue Cause # 5: Food Allergies

While food is sup­posed to give us energy, some doc­tors believe hid­den food intol­er­ances — or aller­gies — can do the oppo­site. Accord­ing to Rudy Rivera, MD, author of Your Hid­den Food Aller­gies Are Mak­ing You Fat, even mild food intol­er­ance can leave you feel­ing sleepy. Eat the offend­ing food long enough and you could find your­self feel­ing con­tin­u­ally exhausted.

“Evi­dence indi­cates food intol­er­ance as a cause of fatigue, and even sug­gests that fatigue may be an early warn­ing sign of food intol­er­ance,” he says.

If you sus­pect that food may be behind all that yawn­ing, Rivera says to start with an elim­i­na­tion diet, cut­ting out foods that cause you to feel sleepy within 10 to 30 min­utes of eat­ing them. You can also talk to your doc­tor about a food allergy test — or invest in a home test such as ALCAT — which may help you iden­tify the offend­ing foods.

Fatigue Cause # 6: Sleep Apnea

If you’re not get­ting enough sleep, it stands to rea­son you’ll be tired. But what if you don’t know that you aren’t get­ting suf­fi­cient sleep? This is often the case with a con­di­tion called sleep apnea — a sleep dis­or­der that causes you to momen­tar­ily stop breath­ing, often many times dur­ing the night. Each time you stop breath­ing, you awaken just long enough to dis­rupt your sleep cycle, usu­ally with­out being aware of it. Your only clue, says Gold­berg, is that you expe­ri­ence con­stant fatigue no mat­ter how many hours you sleep each night.

Accord­ing to Gold­berg, sleep apnea, which is caused by an upper air­way obstruc­tion, often occurs in women who are over­weight or obese. Snor­ing is often a sign of sleep apnea. Diag­no­sis requires a visit to a sleep lab, or to a doc­tor spe­cial­iz­ing in sleep apnea.

If you have sleep apnea, your physi­cian will rec­om­mend lifestyle changes, includ­ing los­ing weight and quit­ting smok­ing. Med­ical treat­ment includes devices that keep air­way pas­sages open while you sleep. In extreme cases, surgery may be nec­es­sary to ensure proper air­way flow. Left untreated, sleep apnea can increase your risk of stroke or heart attack.

Fatigue Cause # 7: Undi­ag­nosed Heart Disease

If you find your­self becom­ing exhausted after activ­ity that used to be easy, it may be time to talk to your doc­tor about the pos­si­bil­ity of heart disease.

Accord­ing to Gold­berg, when over­whelm­ing fatigue sets in after ordi­nary tasks — such as vac­u­um­ing the house, doing yard work, or com­mut­ing from work each day — your heart may be send­ing out an SOS that it needs med­ical attention.

“This doesn’t mean that you should panic every time you yawn,” says Gold­berg. “Most of the time, fatigue is not the first sign of heart dis­ease, and it’s usu­ally linked to some­thing far less serious.”

At the same time, Gold­berg points out that heart dis­ease is the lead­ing cause of death in women. “If fatigue fol­low­ing activ­ity is sig­nif­i­cant, and no other pos­si­ble rea­son comes to mind, see your doc­tor for a check-up,” she advises. If your fatigue is related to your heart, med­ica­tion or treat­ment pro­ce­dures can usu­ally help cor­rect the prob­lem, reduce the fatigue, and restore your energy.