Editor’s Note:
This article is shared for general informational and educational purposes only. It is not intended to replace professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay seeking it because of something you have read here.
Hydration and Dehydration
Common Symptoms of Dehydration
You may be experiencing dehydration if you notice any of the following:
- Dry or sticky mouth
- Unexplained sleepiness or fatigue
- Dry skin
- Frequent headaches (without another established cause)
- Lightheadedness (not to be confused with vertigo or giddiness)
- Muscle cramps or unexplained aches and pains
- Difficulty feeling refreshed, even after adequate sleep
- Constipation or irregular bowel movements
If you recognise several of these symptoms and your daily water intake is consistently low, increasing your fluid intake is a reasonable first step. However, these symptoms can also indicate other medical conditions, and you should consult a doctor if symptoms are persistent, severe, or unexplained.
How Much Water Do You Need?
Hydration needs vary depending on body size, activity level, climate, and overall health. A commonly cited general guideline is around 8 cups (approximately 2 litres) of water per day for most adults, though individual needs may be higher — for example, during strenuous exercise, in hot climates, or with certain medical conditions. Your doctor or dietitian can provide personalised guidance.
Why Do People Become Dehydrated?
Modern lifestyles contribute to inadequate fluid intake. Some people simply forget to drink water throughout the day. Others may limit intake deliberately — for example, due to concerns about restroom access during work — without realising the potential health consequences.
The body loses fluids constantly, even during routine activities, through breathing, perspiration, and urination. Factors that can increase fluid loss and dehydration risk include:
- Staying in air-conditioned environments for extended periods
- Strenuous physical activity without adequate fluid replacement
- Frequent long-haul flights (particularly relevant for pilots and flight crew)
- Excessive alcohol consumption
- High-altitude environments
- Physical illness, including vomiting and diarrhoea
It is worth noting that dehydration can be present in someone who appears outwardly well. This is sometimes called “subclinical” or mild dehydration.
IV Hydration Therapy
The most accessible and recommended approach to maintaining hydration is simply drinking adequate fluids throughout the day. However, in cases of significant or rapid dehydration — for example, following illness, intense physical exertion, or long travel — intravenous (IV) hydration therapy can be used to replenish fluids and electrolytes more quickly than oral intake allows.
IV hydration should be administered by a qualified medical professional, and is most appropriate when oral hydration is insufficient or not possible. It is not a substitute for regular daily fluid intake.
Nutritional Deficiency and Chronic Fatigue
Symptoms of Nutritional Deficiency
Persistent nutritional deficiencies — particularly of vitamins and minerals — can contribute to a range of symptoms, including:
- Unusual or unexplained tiredness and sleepiness
- Short-term memory difficulties
- Poor concentration
- Unexplained muscle or joint pain
- Frequent mild headaches
- Feeling unrefreshed after sleep
- Excessive exhaustion following physical activity, beyond what would normally be expected
- “Brain fog” — a subjective sense of mental cloudiness, poor short-term memory, or difficulty thinking clearly
These symptoms overlap with many conditions, including Chronic Fatigue Syndrome (CFS/ME), thyroid disorders, anaemia, and depression. If you are experiencing these symptoms persistently, a medical evaluation is essential to identify the underlying cause.
Why Nutritional Deficiencies Occur
Even people who eat a varied diet can develop deficiencies. Contributing factors include:
- Gastrointestinal conditions that impair nutrient absorption
- Certain medications (discussed further below)
- Restrictive diets (e.g., vegan or vegetarian diets lacking supplementation)
- Ageing, which affects stomach acid production and nutrient absorption
- Chronic illness
Regarding food quality: there is ongoing scientific research into how farming practices — including the use of pesticides and chemical fertilisers — may affect the nutritional content of produce and potential toxin exposure. The evidence in this area continues to evolve. What is well established is that eating a varied diet of whole foods remains beneficial, and washing produce thoroughly is advisable.
Vitamin B12 Deficiency
Why B12 Matters
Vitamin B12 is essential for the healthy functioning of the nervous system, red blood cell production, and DNA synthesis. Deficiency — if left untreated — can lead to serious and potentially irreversible neurological complications. Early identification and treatment are important.
Who Is at Risk?
The main dietary sources of Vitamin B12 are animal products, including meat, fish, dairy, and eggs. As a result, the following groups are at increased risk of deficiency:
- Vegans and vegetarians who do not supplement
- People with fish, meat, or shellfish allergies
- Older adults (reduced stomach acid impairs B12 absorption)
- People with gastrointestinal conditions such as pernicious anaemia, Crohn’s disease, or those who have had gastric surgery
- People taking certain medications long-term (see below)
Medications Associated with Low B12
Several commonly prescribed medications have been associated with reduced B12 levels, primarily through effects on absorption:
- Metformin (used for type 2 diabetes) — well-established association
- Proton pump inhibitors (e.g., omeprazole, lansoprazole) and H2 blockers (e.g., ranitidine) — reduce stomach acid needed for B12 absorption
- Oral contraceptive pills — some studies suggest a possible association; evidence is less definitive
- Certain chemotherapy agents — may affect B12 metabolism
If you are taking any of these medications long-term, it is worth discussing B12 monitoring with your doctor.
Reference Ranges for B12
Normal serum B12 levels vary by laboratory, but are typically reported in the range of approximately 160–950 pg/mL (picograms per millilitre), with specific thresholds differing between labs and clinical guidelines. Interpretation should always be done in the context of clinical symptoms, as neurological symptoms can sometimes occur even with levels in the lower-normal range.
Neurological Effects of Severe B12 Deficiency
If left untreated for a prolonged period, severe B12 deficiency can cause progressive neurological damage, including peripheral neuropathy (numbness, tingling, and balance problems), subacute combined degeneration of the spinal cord, cognitive decline, and in rare and extreme cases, more severe neurological impairment. Some presentations can mimic other conditions such as dementia or movement disorders.
The critical point is that these outcomes are largely preventable with timely diagnosis and treatment. Patients and clinicians should be alert to the possibility of B12 deficiency, particularly in the groups at risk described above.
Vitamin C and the Immune System
Vitamin C plays an important role in immune function, and deficiency has been associated with increased susceptibility to infections. It also acts as an antioxidant, helping to neutralise damaging free radical molecules in the body. Most people who eat a diet containing adequate fruits and vegetables will maintain sufficient levels, but supplementation may be appropriate in some cases — discuss this with your doctor or dietitian.
Treatment: Oral Supplementation vs. Injections vs. IV Infusion
For mild to moderate vitamin deficiencies in individuals without absorption problems, oral supplementation — taken consistently at appropriate doses — is effective for most people. High-dose oral B12 (cyanocobalamin), for example, can be absorbed even in people with reduced intrinsic factor through passive diffusion, and is considered a valid treatment option in many guidelines.
Intramuscular (IM) injections of B12 are the most established medical approach for deficiency associated with absorption problems (e.g., pernicious anaemia), and have a strong evidence base.
Intravenous (IV) infusion delivers vitamins and minerals directly to the bloodstream, bypassing the gastrointestinal tract entirely. This may be particularly appropriate for patients with significant absorption impairment or those requiring rapid correction of severe deficiency. IV infusion therapies should be administered by qualified medical professionals in appropriate clinical settings.
The right approach depends on your individual circumstances, the severity of any deficiency, and the underlying cause. A medical professional should guide this decision.
A Final Note
The goal of this article is to raise awareness of dehydration and nutritional deficiencies as underappreciated contributors to common symptoms — and to encourage people to take these factors seriously. However, awareness should always be paired with professional evaluation. If you are experiencing persistent or concerning symptoms, please see a qualified healthcare provider rather than self-diagnosing or self-treating based on any article, including this one.
Original article by Dr. Gurusamy Asogan, MBBS, FCGP, Universal Care Clinic. Editorially reviewed and revised for general informational accuracy.
