Conditions
Dehydration in adults: symptoms, oral rehydration and when to go to the ER
Dehydration in adults happens when you lose more fluid than you take in, from sweating in the heat, vomiting, diarrhea or fever. It causes thirst, a dry mouth, less and darker urine, headache and cramps. Mild dehydration is treated with sips of water and oral rehydration solution. By video, our doctor looks for the cause and plans your rehydration; confusion or fainting is an emergency.
Is it an emergency? Call 911.
Is this an emergency?
This is not an emergency service. Call 911 or go to the nearest emergency room if you have:
- Confusion, seizures or any change in alertness
- Fainting or loss of consciousness
- Not peeing, or very dark, amber-colored urine
- An older adult, or any adult, who can’t keep fluids down
- A fever over 102 °F (38.8 °C) with signs of dehydration
- Symptoms that get worse or don’t improve even though you are drinking
Help lines
At a glance
Dehydration
Common symptoms
- Thirst
- Dry mouth
- Peeing less than usual
- Dark yellow urine
- Headache
- Muscle cramps
- Other names
- Dehydration in adults
- Treatment
- Fluids by mouth with electrolytes (oral rehydration solution); IV fluids in person when severe
- Possible complication
- Severe dehydration with confusion, fainting or shock
On this page(10)
What is dehydration?
Dehydration means your body doesn’t have as much water and fluid as it needs. According to MedlinePlus, it happens because you lose too much fluid, don’t drink enough, or both.
Common causes are heavy sweating, for example when you exercise or work in the heat; fever; vomiting and diarrhea, as with a stomach bug; urinating too much; and being unable to drink because of nausea or a sore mouth or throat. Older adults and people with diabetes are at higher risk.
How we treat dehydration in adults by video
You see Dr. Diana Nieves Castro, a Puerto Rico–licensed general practice physician with several years of emergency-department experience, in English or Spanish. We evaluate, diagnose and treat: the doctor asks what caused the fluid loss, how much you can drink, how much and what color you pee, and what medicines you take, and observes you on camera.
If the dehydration is mild or moderate and you can keep fluids down, she gives you a plan to rehydrate at home and treats the cause. If needed, we give you a lab order for a lab near you. If appropriate, the doctor prescribes and we send your prescription to your pharmacy. We do not prescribe controlled substances. If you need IV fluids, that happens in person, and the doctor tells you where to go.
This is urgent care by video for problems that are not emergencies. You need to be physically in Puerto Rico during the visit; visitors are welcome.
Your doctor
Dr. Diana Nieves Castro, MD
General practice physician
Several years of emergency-department experience.
Founding Executive Director of The Health Initiative.
Your visit in 3 steps
Request a visit online 24/7 — we confirm your time by email or text.
Request your visit and pay by card. Choose Doctor visit.
We send you a secure video link. It works on your phone, tablet or computer.
The doctor evaluates you and gives you a plan. If appropriate, she prescribes and we send your prescription to your pharmacy; if needed, you get a lab order.
What the visit costs
A doctor visit costs US$79, the same price for every age, with no membership. Your card is charged when you request the visit, and you get a full refund if the visit can’t take place. A doctor’s note after your visit is included at no extra charge. The service is run by The Health Initiative, a nonprofit. Book your visit.
Dehydration symptoms
According to MedlinePlus, mild to moderate dehydration causes:
- Thirst
- Dry mouth
- Peeing less than usual
- Dark yellow urine
- Headache
- Muscle cramps
Severe dehydration
MedlinePlus describes severe dehydration as:
- Not peeing, or very dark yellow or amber-colored urine
- Confusion or marked dizziness
- Fast heartbeat and fast breathing
- Sunken eyes
- Fainting or loss of consciousness
Treatment: oral rehydration, and when a test is ordered
For mild dehydration, MedlinePlus advises sipping water or sucking on ice chips, and drinking water or sports drinks with electrolytes. Oral rehydration salts, powders you mix with water that are sold at pharmacies, replace the salts and minerals you have lost. Drink small amounts often, especially if you feel sick to your stomach. If you also get muscle cramps or feel dizzy when you stand up, see low blood pressure too.
Don’t take salt tablets: MedlinePlus warns they can cause serious complications. If you have diabetes, high blood pressure, a low-salt diet or another chronic condition, Puerto Rico’s Department of Health advises checking with your doctor before using sports drinks.
If vomiting or diarrhea won’t stop, if you take diuretics or other medicines that affect fluids, or if you have diabetes, the doctor may order blood or urine tests; we give you a lab order for a lab near you and go over the result with you.
Dehydration in older adults and in children
MedlinePlus notes that older adults are at higher risk of dehydration, and advises paying close attention to how much children and older adults drink when someone in the family is ill. If you care for an older adult who can’t keep fluids down, don’t wait: take them to the ER.
For babies and children, read diarrhea and vomiting in children, which covers the signs of dehydration by age. If the heat caused it, read about heat exhaustion and heat stroke.
When to go to the ER
For your safety, with any of these signs call 911 or go to an emergency room. See when to go to the ER.
- Confusion, seizures or any change in alertness
- Fainting or loss of consciousness
- Not peeing, or very dark, amber-colored urine
- An older adult, or any adult, who can’t keep fluids down
- A fever over 102 °F (38.8 °C) with signs of dehydration
- Symptoms that get worse or don’t improve even though you are drinking
How we care for you
We evaluate, diagnose and treat; if needed, we give you a lab order for a lab near you.
We see adults and children of all ages. Patients under 21: a parent with patria potestad (parental authority) or a legal guardian is on camera for the whole visit and shows photo ID.
Real-time video visit. We send you a secure video link. It works on your phone, tablet or computer.
If appropriate, the doctor prescribes and we send your prescription to your pharmacy. We do not prescribe controlled substances.
You must be physically in Puerto Rico during the visit (visitors, tourists and cruise passengers are welcome).
In an emergency, call 911.
Frequently asked questions
How do I know if I am dehydrated?
What should I drink for dehydration?
Can I get IV fluids through a video visit?
Do you treat dehydration in children?
Can I get dehydrated after drinking alcohol?
About this page
Author: The Health Initiative
Medical care provided by Dr. Diana Nieves Castro, MD (PR license 24027)
Disclosure: Founding Executive Director of The Health Initiative
Published: 2026-10-02 · Updated: 2026-10-02
Sources (6)
- Dehydration (MedlinePlus, NIH) (opens in a new tab) (accessed 2026-10-02)
- Dehydration: health topic (MedlinePlus, NIH) (opens in a new tab) (accessed 2026-10-02)
- Dehydration (NHS) (opens in a new tab) (accessed 2026-10-02)
- Informe de mensajería sindrómica: eventos relacionados al calor o la luz, semana 36, 2026 (Puerto Rico Department of Health, in Spanish) (opens in a new tab) (accessed 2026-10-02)
- Heat and medications: guidance for clinicians (CDC) (opens in a new tab) (accessed 2026-10-02)
- Hangovers (NIAAA, NIH) (opens in a new tab) (accessed 2026-10-02)