Why You Swell When You Wake Up: A Discussion on Swelling and Fluid Metabolism

When you wake up in the morning, your eyelids feel heavy, and your facial contours seem blurred. Rings are hard to remove, and your finger joints feel stiff. However, by the afternoon, your face looks normal, but your shoes feel tight on your way home from work. The swelling in the same body shifts its location depending on the time of day.

It's easy to dismiss swelling by saying, "I drank too much water yesterday," but what happens in the body is a bit different. Edema (浮腫) is a condition where fluid leaks out of capillaries and accumulates in the tissues. The issue isn't the total amount of water, but where the water resides. This leads to two distinct categories: swelling that resolves on its own within a few days, and swelling that necessitates investigating underlying causes.

Why Your Face Swells in the Morning and Legs in the Evening

During the day, most of us are standing or sitting. Gravity acts in one direction, causing fluid to accumulate in the lower legs and ankles. Evening leg swelling originates from this.

The moment you lie down at night, this dynamic reverses. The article "Diagnosis and Treatment of Edema" published in the 『Journal of the Korean Internal Medicine Society』 explains the process: When lying down, fluid accumulated in the extremities moves towards the heart, increasing cardiac output. Consequently, renal blood flow increases, leading to increased salt excretion. This is why bed rest is a fundamental part of edema treatment, and needing to go to the bathroom at night is also part of the same physiological process.

However, not all the shifted fluid is excreted as urine. The portion remaining in the facial area during sleep manifests as morning puffiness, and it moves downwards again after a few hours of activity upon waking. Most swelling that changes location throughout the day can be explained by this redistribution.

Pressing Reveals the Difference

There's a simple way to check for edema. Press the area above the bone on the front of your calf with your finger for a few seconds. If the pressed area indents and slowly returns to normal, it's pitting edema.

If it's non-pitting edema, where pressing doesn't cause an indentation, the situation is different. The aforementioned paper suggests that in such cases, lymphedema or myxedema should be considered, and it may not respond well to diuretics. Myxedema is swelling that occurs in hypothyroidism. This means that "swelling that doesn't go away easily" might not be a matter of effort but a signal of a different type.

The causes of generalized edema can be broadly categorized into three organ systems. Right heart failure causes peripheral edema, while left heart failure is mainly accompanied by pulmonary edema. Liver cirrhosis typically presents with ascites and lower extremity edema; a key difference from right heart failure is that central venous pressure is normal or even low in this condition. Nephrotic syndrome is characterized by periorbital edema and is diagnosed when proteinuria exceeding 2.5 g per day, hypoalbuminemia, and hyperlipidemia are present.

Medications can also be a cause. The same paper lists analgesics, oral contraceptives, antihypertensives, and steroids as common culprits for causing edema. If swelling began after starting a new medication, it's advisable to note the timing. Cyclical swelling, such as premenstrual edema, is explained by fluid and salt retention due to estrogen.

This Isn't Just Swelling; It's a Medical Signal

There's a crucial point to emphasize here:

Seek immediate medical attention if one leg suddenly swells, you experience shortness of breath, or your weight increases rapidly within a few days.

The article "Diagnosis and Treatment of Edema" explicitly states when discussing venous insufficiency, "Patients with sudden, unexplained unilateral leg swelling must be evaluated for deep vein thrombosis." According to Seoul National University Hospital's medical information, deep vein thrombosis can manifest as changes in leg color, sudden swelling, and calf pain during walking. The most fatal complication is pulmonary embolism, where a clot travels to the pulmonary artery. Risk factors include prolonged sitting or lying down, post-surgery, pregnancy, malignancy, and obesity.

Shortness of breath, especially when lying down, suggests pulmonary edema, most commonly caused by heart disease. Rapid weight gain directly reflects fluid retention. If any of these three signs are present, medical evaluation should precede lifestyle management or herbal remedies.

Self-medicating with diuretics is also not recommended. Idiopathic edema is commonly found in women aged 30-50. The paper notes that many of these patients have a history of excessive dieting or prolonged diuretic use. In such cases, the first course of treatment is discontinuing the diuretic.

The Number 3,030 mg Per Day

Sodium retains water. The "Trend of Sodium Intake, 2013–2022" compiled by the Korea Disease Control and Prevention Agency (KDCA) using data from the Korea National Health and Nutrition Examination Survey shows that the average daily sodium intake for Koreans in 2022 was 3,030 mg. Although there has been a downward trend since 2013, this is still 1.5 times the target intake of 2,000 mg set by the same agency for comparison. Intake is higher in men than in women, and consumption is highest among those in their 30s and 40s.

However, it's important to have realistic expectations. The aforementioned paper from the Korean Society of Internal Medicine clearly states that edema does not easily resolve with a low-sodium diet. The role of a low-sodium diet is to prevent the worsening of edema and enhance the effectiveness of diuretics when needed. If swelling persists after a day or two of eating bland food, it's not a failure but an indication that it doesn't work that way. Reducing water intake is also misguided. If sodium retention is the underlying issue, it's the salt, not the water, that needs to be reduced.

Korean Medicine Views It Through the Lens of Fluid Retention and Spleen Deficiency

Korean medicine also addresses edema, but uses different terminology. The article "Clinical Research Trends on Traditional Korean Medicine Treatment for Idiopathic Edema" published in the 『Journal of Korean Traditional Internal Medicine』 views idiopathic edema as a disorder of Qi transformation (氣化) due to functional imbalance of the three organs—Lung (肺), Spleen (脾), and Kidney (腎). It further explains that this is intertwined with Liver Qi stagnation (肝氣鬱滯) and improper function of the Triple Burner's water pathways (三焦水道不利), leading to fluid retention and blood stasis (瘀血). Spleen deficiency (脾虛) refers to a weakened digestive, absorptive, and fluid transport function, while fluid retention (水毒) signifies stagnant, unused water within the body. These are frameworks for categorizing bodily states, not diagnostic labels for diseases.

The same paper analyzed 16 literature reviews (7 randomized controlled trials, 2 non-randomized studies, and 7 case studies). Among the prescriptions, Oren-san (五苓散) was the most frequent, appearing 7 times. The herbs most commonly used were Poria cocos (복령), Atractylodes macrocephala (백출), and Alisma orientale (택사), each appearing 12 times, followed by Polyporus umbellatus (저령) 11 times, and Cinnamon (계지) and Astragalus (황기), each 10 times. These belong to the category called "diuretics" (이수).

However, the sample sizes are small, and the research is primarily based on Chinese literature, so the level of evidence is still limited.

There is also research on the mechanism. The article "Analysis of Literature on the Efficacy of Oren-san in Basic Experimental Studies" from the same journal reviewed a total of 57 studies (16 from Korea, 17 from China, and 24 from Japan). It summarized findings where Oren-san administration led to decreased expression of Aquaporin (AQP2, AQP3) mRNA in the kidneys, resulting in increased urine output. Aquaporins are channel proteins that facilitate water transport across cell membranes. However, these are results from animal studies and may not directly apply to humans.

The order of approach is as follows: first, screen for warning signs; second, confirm the absence of underlying diseases; and third, implement lifestyle management. Jaimdang's Gongmicha falls into this last category. It is a food product (tea) containing ingredients like corn silk and is not intended for the prevention or treatment of diseases.

If weight management and a tendency to swell are concerns, prescriptions like Gongbihwan may be considered. This is different in nature. It is a prescription herbal medicine (의약품) that requires consultation and prescription from a Korean medicine doctor to determine if it should be taken; it is not something you choose yourself. Preparation is done at an external herbal medicine preparation center in Paju, Gyeonggi Province. The process involves quantifying marker components of standardized herbs using HPLC, self-testing for heavy metals and pesticide residues, and then decocting under controlled temperature, time, and pressure using a standardized process. Quality control tests are performed for each batch, and lot numbers are attached to the stick pouches. The process is detailed in the article "External Herbal Medicine Preparation Centers and Herbal Medicine Quality" [/ko/journal/wonoe-tangjeon-quality].

If you are taking any medications, you must inform us of the ingredient names and dosages during the consultation. Antihypertensives, steroids, and oral contraceptives themselves can be a background cause of edema, and in such cases, consultation with your attending physician is necessary before any arbitrary discontinuation. The procedure is outlined in "Non-Face-to-Face Herbal Medicine Prescription Guide" [/ko/journal/bidaemyeon-hanyak-guide].

Four Things to Check Starting Tonight

• Check if it's bilateral or unilateral — If only one leg suddenly swells and the calf is painful, it's a medical emergency, not a lifestyle management issue.
• Record your morning weight under the same conditions — Immediately after waking up and using the restroom, wearing the same clothing. A rapid increase over a few days is the most honest indicator.
• Press and check for indentations — Press the front of your calf for a few seconds and note if an indentation remains, or if it doesn't indent at all. This information is useful during medical consultations.
• Note any new medications and frequency of consuming broths — Record the start date of analgesics, oral contraceptives, blood pressure medications, or steroids, and track your daily soup and stew intake for a week.

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References

• Kim Seung-jeong, "Diagnosis and Treatment of Edema", *The Korean Journal of Medicine*, 69(5), 2005
• Chronic Disease Management Bureau, Health and Nutrition Survey Analysis Division, KDCA, "Trend of Sodium Intake, 2013–2022", *Weekly Health & Disease*, 17(16), 2024
• Seoul National University Hospital Medical Information, "Deep Vein Thrombosis"
• Park Mi-so et al., "Clinical Research Trends on Traditional Korean Medicine Treatment for Idiopathic Edema — Focusing on CNKI Search", *Journal of Korean Traditional Internal Medicine*, 43(4), 2022
• Kim Jeong-hoon & Shin Hyung-gyu, "Analysis of Literature on the Efficacy of Oren-san in Basic Experimental Studies", *Journal of Korean Traditional Internal Medicine*, 33(1), 2012

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*This article is intended for informational purposes regarding edema and fluid metabolism and does not guarantee the diagnosis or treatment efficacy for any specific condition. Gongmicha is a food product and is not intended for the prevention or treatment of diseases. Gongbihwan is a prescription herbal medicine determined by a Korean medicine doctor's consultation and prescription; individual responses may vary. If you experience sudden swelling in one leg, shortness of breath, or rapid weight gain, seek medical attention without delay.*