Brief Answer:
Depletion of electrolytes.

Detailed Answer:
Hi,
Thank you for choosing HealthcareMagic for your query,

Before answering the cause of weakness Let me first give you a brief idea about why are you having your symptoms,

You had diarrhea which lasted for 1 week, a prolonged bout of diarrhea or vomiting can cause the body to lose more fluid than it can take in. The result is dehydration, which occurs when your body doesn't have the fluid it needs to function properly; usually, dehydration plays a major role in fatigue and extreme weakness with drowsiness.

If your blood volume is up to normal, your body can circulate enough fluid to your muscles and viscera to keep you functioning, this circulating fluid is responsible for maintaining the activity of the body. As the blood volume decreases, as, in diarrhea, blood flow throughout the body decreases leading to severe fatigue and pain(as electrolytes are supplied by blood)


Severe fatigue joint pains aches etc are because of dehydration,during diarrhea body looses a large amount of electrolyte in stools and vomiting, an imbalance between electrolytes like sodium, potassium may trigger these symptoms and can cause easy fatiguability.

Feeling tired and having pain all the time is also because your body is depleted of important electrolytes, and you have not compensated for the lose of those electrolytes by taking extra electrolytes in form of oral rehydration solution externally.

Your symptoms right now are due to gastroenteritis overlapped with dyspepsia and gastritis.

As your age is 61 the effect of depletion of the electrolyte is more pronounced in your case.

Advice:
Drink plenty of water
Add electrolytes (Electral: electrolyte powder ) to water and drink as much as possible, this will immediately restore the depleted electrolytes.

If the electral powder is not available right now add a pinch of salt & teaspoon of sugar to water & drink.

Eat banana, pear, coconut water and orange juice they are very rich in potassium and will relieve your symptoms immediately.

As soon as your body get rehydrated and depleted electrolytes are restored again, all your symptoms like fatigue, tiredness, hypothermia and headache will go away.

Take light food as you are already taking, keep salt in food on the higher side.

Probiotics should be taken for at least 5 days to restore the gut flora again, once restored your appetite will return to normal again.

Digestive enzymes can also be taken for few days

Take Imodium for loose stools and Nexium with Peptobismol for heartburn and gastritis.
You can consult your physician for the doses and further evaluation.

If you have any other query, feel free to ask me, I would be happy to help you!

Thank you

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