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Dr. Chrysoula I. Liakou MD, PhD
- Treated online: Yes, for assessment, tests and follow-up. Deficiencies, an underactive thyroid and type 2 diabetes are assessed by video, tested at a laboratory near you and treated or referred on the results; an overactive thyroid, suspected type 1 diabetes and rare diseases go to a specialist.
- What it is: a nutrient or fuel the body lacks or cannot use: iron deficiency affects about 1 in 4 younger women, low vitamin D 1 in 5 adults in winter, an underactive thyroid 1 in 50, and type 2 diabetes about 1 in 12 European adults.
- Blood tests: a blood count and ferritin, vitamin B12 and folate, vitamin D, thyroid function, HbA1c for blood sugar, a lipid profile and a coeliac screen find most nutrition and metabolism disorders in one sitting; symptoms alone cannot tell them apart.
- Timelines: iron stores take 3 to 6 months of tablets to refill, B12 injections lift energy within weeks, vitamin D levels correct over 2 to 3 months, thyroid tablets take 6 to 8 weeks to show their full effect, and HbA1c reflects the previous 3 months.
- Supplements: self-prescribed high-dose supplements can be wasteful or harmful (too much vitamin A, iron or vitamin D) and mask the real cause; test first, then treat what is low at the right dose for the right time.
- Emergency: call 112 for very high blood sugar with drowsiness, deep or rapid breathing or fruity-smelling breath, for very low blood sugar with confusion or collapse that does not respond to sugar, or for a racing irregular heartbeat with fainting.
Some metabolic problems can become urgent. Call 112 or attend emergency care if you have very high blood sugar with drowsiness, deep or rapid breathing, fruity-smelling breath or confusion, or signs of very low blood sugar (shaking, sweating, confusion or collapse) that does not respond to sugar. Rapid unexplained weight loss, fainting, a racing or irregular heartbeat, or severe muscle weakness need prompt in-person assessment rather than an online consultation.
Can an online doctor help with nutrition and metabolism disorders?
Yes, as a first assessment and a route to the right tests, rather than as a place that treats every metabolic disease online. A licensed doctor can review symptoms such as tiredness, weight change or excessive thirst, decide which blood tests are needed (thyroid, glucose, iron, vitamin B12, folate, vitamin D and others), and then either start treatment or refer you.[1] Complex or rare metabolic diseases need specialist care.
This is deliberately an assess-and-refer page rather than a cure-all promise. The umbrella covers everything from a simple iron deficiency to inherited metabolic conditions, and no honest online service treats all of that by video. What it can do reliably is sort your symptoms, order the tests that answer the question, and get you onto the correct pathway quickly.
How an online consultation helps
- Making sense of vague symptoms: tiredness, weight change, feeling cold, thirst or low mood have many causes, and the doctor sorts which point towards a nutritional or metabolic problem worth testing.[2]
- Ordering the right blood tests: rather than a scattergun panel, the doctor selects the tests your story actually calls for and explains what each one is checking.
- Starting the simple things: confirmed deficiencies and common problems such as an underactive thyroid can often be started or managed after the results are back, with a clear review plan.[2]
- Honest, fast referral: where the picture points to specialist territory (complex diabetes, endocrine disease, or a rare metabolic disorder), the doctor says so and directs you, rather than stretching an online consultation past its limits.
What the doctor checks in an online nutrition and metabolism consultation
Because this is an umbrella of conditions, the consultation is a structured sorting exercise. The doctor will typically establish:
- Your main symptoms and their timeline: fatigue, weight gain or loss, thirst and urination, temperature intolerance, hair or skin changes, mood, and how quickly they have developed.
- Diet and absorption: your eating pattern, any restrictive or vegan diet, alcohol intake, and gut conditions or surgery that affect how you absorb nutrients, since deficiencies often start there.[1]
- Risk factors: family history of diabetes, thyroid or metabolic disease, pregnancy, age, and medicines that affect metabolism or nutrient levels.
- Thyroid and endocrine clues: features suggesting an underactive or overactive thyroid, and other hormonal patterns worth testing.[2]
- Blood-sugar signals: excessive thirst, frequent urination, unexplained weight loss and fatigue, which together raise the question of diabetes and prompt glucose testing.[3]
- Red and amber flags: rapid weight loss, fainting, palpitations, or symptoms of a metabolic emergency that move you straight to in-person care.
- What has been tested before: recent blood results, so the plan builds on them rather than repeating them.
What counts as a nutrition or metabolism disorder?
It is a broad family of conditions in which the body's supply of nutrients or its handling of energy goes wrong. Grouping them helps show where an online doctor fits.
Nutritional deficiencies
Shortfalls of iron, vitamin B12, folate or vitamin D are among the most common and the most treatable. They cause tiredness, breathlessness, pins and needles, mouth or tongue changes, or bone and muscle aches, and they are confirmed on a blood test and corrected with diet or supplements.[1][4] Poor absorption, for example from coeliac disease or after gut surgery, is a frequent hidden cause, which is why the doctor asks about your digestion.
Thyroid and other endocrine problems
The thyroid sets your metabolic pace. An underactive thyroid causes fatigue, weight gain, feeling cold and low mood; an overactive one causes weight loss, a racing heart, heat intolerance and anxiety. Both are diagnosed on thyroid blood tests, and an underactive thyroid in particular is commonly managed in general practice once confirmed.[2]
Diabetes and blood-sugar disorders
Diabetes is the metabolic disorder people know best. The warning signals (increased thirst, passing more urine, unexplained weight loss, tiredness and blurred vision) deserve prompt testing, because early diagnosis changes the outlook. Type 2 diabetes is often identified and managed in primary care, while type 1 and complex cases need specialist input.[3] Rarer inherited conditions of metabolism (such as those affecting how the body handles specific sugars, fats or minerals) sit firmly in specialist care.
Why blood tests are central
Almost every condition in this group is confirmed or excluded by a blood test, not by examination alone, which shapes how the online pathway works. The doctor's job in the consultation is to decide which tests your symptoms justify, arrange them, and interpret the results with you, rather than to guess a diagnosis from the outside. Your doctor tells you where to have the blood drawn. Once results are back, some conditions can be treated directly, while others define a clear referral. Being upfront about that sequence is the whole point of an assess-and-refer page: the value is an accurate first step and the right test, not a promise to fix everything by video.
What can be handled online, and what is referred?
This is the heart of the page. This is the framework the doctors use to decide, aligned with the cited guidance.
Swipe sideways to compare →
| Presentation | Likely first step | Suitable for online care? | When referral or in-person care is needed |
|---|---|---|---|
| Tiredness or symptoms suggesting a common deficiency (iron, B12, folate, vitamin D) | Targeted blood tests, then diet or supplement treatment[1] | Usually yes | Severe deficiency, no response, or an underlying cause needing investigation |
| Symptoms of an underactive thyroid | Thyroid blood tests; start or manage treatment once confirmed[2] | Often yes | Overactive thyroid, pregnancy, or an uncertain or complex result |
| Blood-sugar warning signs (thirst, urination, weight loss) | Glucose testing; assessment for type 2 diabetes[3] | Assessment and often ongoing care | Suspected type 1, very high readings, or complications |
| Suspected rare or inherited metabolic disorder | Assessment and specialist referral | Assessment and referral only | Always: these are managed in specialist metabolic services |
| Metabolic emergency (very high or low blood sugar, collapse) | Emergency care | No | Call 112 or attend urgently |
Not sure which row is you? A doctor can tell you in one consultation.
See available times →Treatment options for nutrition and metabolism disorders
What you can do yourself
A varied diet covers most nutritional bases: iron from red meat, pulses and leafy greens; B12 from animal foods, with fortified foods or supplements important for vegans; vitamin D from sunlight and oily fish, with supplements often sensible in the darker European months.[1][5] Moderating alcohol and keeping active support metabolic health broadly. The honest caveat is this: self-diagnosing a deficiency and buying high-dose supplements online is a poor substitute for a blood test, because the symptoms overlap heavily and some supplements can cause harm in excess. Bring your symptoms to the consultation rather than a self-prescribed cupboard of tablets.
Treatment after your results
A prescription is never issued without a consultation, and in this group it usually follows the blood results rather than the call. Confirmed iron, B12, folate or vitamin D deficiency is corrected with the right dose and form, then rechecked; a confirmed underactive thyroid is treated with thyroid hormone replacement and monitored;[2] and type 2 diabetes is managed with lifestyle change and, where needed, medicines, with ongoing review.[3] Where results point to an overactive thyroid, suspected type 1 diabetes, a complex endocrine problem or a rare metabolic disease, the treatment is specialist, and the doctor arranges referral rather than starting something unsuitable online.
When it might be something else
Tiredness and weight change are famously non-specific, and part of the consultation is keeping the wider picture in view. Persistent digestive symptoms with deficiency can signal malabsorption, which links to conditions such as coeliac disease and is why the doctor may ask about your gut and consider the diarrhoea and constipation assessments. B12 deficiency from an autoimmune stomach condition connects to gastritis. Fatigue can equally reflect poor sleep, low mood, anaemia or a chronic illness, and thirst and weight loss can have causes beyond diabetes. Testing is what separates these, which is why the plan centres on the right bloods rather than a snap label.
When nutrition and metabolism disorders are assessed online, and when you need in-person care
Assessed and often treated online: common nutritional deficiencies confirmed on testing; a confirmed underactive thyroid; assessment of blood-sugar warning signs and ongoing type 2 diabetes care; and interpreting recent results to plan sensible next steps. These are the parts of this umbrella an online GP can plausibly act on, and they cover most people who search for help here. Nutrition and metabolism concerns sit alongside the wider stomach and digestive problems assessments.
In-person care: an overactive thyroid, suspected type 1 diabetes, complex or poorly controlled diabetes, other endocrine disease, and any suspected rare or inherited metabolic disorder are directed to specialist services, because that is where they are properly managed. Anything suggesting a metabolic emergency is exactly that. In those cases the consultation gives you a fast, accurate assessment and the correct referral, with a full refund if your doctor decides you need to be seen in person.
When to get in-person care
Call 112 or attend emergency care immediately if you have very high blood sugar with drowsiness, deep or rapid breathing, fruity-smelling breath or confusion; signs of very low blood sugar that does not respond to sugar; or collapse and severe weakness. Arrange urgent in-person assessment for rapid unexplained weight loss, fainting, a persistently racing or irregular heartbeat, or severe muscle weakness. These need timely examination and tests that an online consultation cannot substitute for.
How Mobi Doctor works
- Book a time that suits you: open daily 7am–11pm CET. You can see a doctor over video, usually within 15 minutes. No subscription, exact price up front.
- Speak to a licensed doctor about nutrition and metabolism disorders: a private video call: you describe what you feel, the doctor asks what matters, and you agree the right plan together.
- Get your test plan and next steps: the right treatment or referral follows once your results are back, and a prescription is never issued without a consultation.
No sign-up needed
Not sure which page fits? Tick every symptom you have to see each condition page that mentions it. It finds the right page, not a diagnosis: a doctor gives you that on a video call.
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Similar symptoms, different condition? Medical Weight Loss can start the same way. Compare them, or look up any other symptom in the full symptom checker.
Frequently asked questions about nutrition and metabolism disorders
What are nutrition and metabolism disorders, and what causes them?
Nutrition and metabolism disorders are conditions in which the body lacks, cannot absorb or cannot use a nutrient or fuel. Deficiencies come from a poor or restricted diet, heavy periods, pregnancy, gut conditions such as coeliac disease that block absorption, weight-loss surgery, alcohol and some medicines; thyroid disorders are usually autoimmune; type 2 diabetes and high cholesterol come from genes plus weight, inactivity and diet; and rare inherited enzyme disorders are found in childhood.
What are the symptoms of a nutrition or metabolism disorder?
Nutrition and metabolism disorders share vague symptoms: tiredness, weakness, breathlessness on stairs, hair loss, brittle nails, pale skin, pins and needles, low mood, poor concentration, feeling cold or hot, weight gain or loss, thirst and frequent urination, muscle aches and bone pain. Because iron, B12, vitamin D, thyroid and blood-sugar problems overlap so heavily, the pattern suggests the tests but only the tests give the diagnosis.
Can an online doctor order blood tests in Europe?
The doctor can advise exactly which blood tests you need for a suspected nutrition or metabolism disorder and tell you where to have them done near you, usually a private laboratory or your local service. Once results are back, they interpret them with you at a follow-up and either start treatment, such as iron, B12, vitamin D or thyroid tablets, or refer you. A prescription is never issued without a consultation.
Can you diagnose a vitamin deficiency online?
Not from symptoms alone. Deficiencies of iron, B12, folate or vitamin D are confirmed on a blood test, because their symptoms overlap heavily with each other and with thyroid disease, depression and sleep problems. The online doctor arranges the right tests, treats a confirmed deficiency at the correct dose and for the correct time, and looks for why it happened, which is often the more important finding.
Can an online doctor help with thyroid or diabetes?
Yes, for much of it. A confirmed underactive thyroid and type 2 diabetes are commonly assessed and managed in primary care, which an online doctor can do with the right tests, reviews and prescriptions, including dose adjustments on blood results. An overactive thyroid, suspected type 1 diabetes, diabetes in pregnancy and complicated cases are referred to an endocrinologist, with the online consultation documenting the findings.
Should I just buy supplements instead of seeing a doctor?
Not before you know what, if anything, is low. Self-prescribed high-dose supplements can be wasteful, occasionally harmful (excess iron, vitamin A or vitamin D), and can mask the real cause of your symptoms, such as a bleeding gut behind iron deficiency or pernicious anaemia behind low B12. A short consultation and the right blood test for a nutrition or metabolism disorder is a far more reliable route than guessing.
How long does it take to correct a deficiency?
Iron stores take three to six months of tablets to refill, though energy often improves within weeks; vitamin B12 injections lift energy and tingling within weeks and continue for life in pernicious anaemia; vitamin D corrects over two to three months, folate within weeks; and thyroid tablets take six to eight weeks to show their full effect, with the dose adjusted on repeat tests. Nutrition and metabolism disorders are re-tested, not assumed fixed.
Which foods help prevent nutrition and metabolism disorders?
Red meat, pulses, dark leafy greens and fortified cereals for iron (with vitamin C to absorb it); meat, fish, eggs, dairy or fortified foods for B12, with a supplement if you are vegan; oily fish, eggs and sunlight for vitamin D, with a supplement from October to March; iodised salt, fish and dairy for the thyroid; and fibre, vegetables and wholegrains with little sugar for blood sugar and cholesterol.
How can I prevent nutrition and metabolism disorders?
Prevent them by eating a varied diet with the food groups above, taking a vitamin D supplement through the winter, planning B12 and iron if you are vegan or vegetarian, treating heavy periods, limiting alcohol, keeping weight and activity in a healthy range to prevent type 2 diabetes, having a blood-sugar and cholesterol check from 40 or earlier with a family history, and having thyroid and coeliac tests if symptoms or family history suggest them.
Are these disorders different in pregnancy, in older people or for vegans?
In pregnancy, iron, folate and vitamin D needs rise and thyroid function matters for the baby's development, so deficiencies are tested and treated promptly and folic acid starts before conception. In older people, B12 and vitamin D deficiency, an underactive thyroid and diabetes are common and present as tiredness, falls or confusion. Vegans need a reliable B12 source for life and often iron, iodine and vitamin D supplements.
Why is this filed under stomach and digestive problems?
Many nutrition and metabolism disorders begin in the gut, through how well you absorb nutrients: coeliac disease, Crohn's disease, weight-loss surgery, low stomach acid and some medicines all block absorption of iron, B12, folate and vitamin D, so there is a genuine overlap. If your symptoms point clearly to a thyroid, blood-sugar or other cause, the doctor focuses there and refers on where specialist care is needed.
When does a nutrition or metabolism problem need urgent in-person care?
A metabolic problem needs urgent care for very high blood sugar with drowsiness, deep breathing or fruity breath, for low blood sugar that does not respond to sugar, for rapid unexplained weight loss, fainting, a racing or irregular heartbeat, severe muscle weakness, or severe anaemia with breathlessness at rest and chest pain. Those patterns are emergencies or need same-visit tests rather than an online consultation; everything milder suits video assessment.
- Malnutrition: fact sheet, WHO, World Health Organization, 2024.
- Hypothyroidism: Clinical Knowledge Summary, NICE, National Institute for Health and Care Excellence, 2024.
- Type 2 diabetes in adults: management (NG28), NICE, National Institute for Health and Care Excellence, 2015 (updated 2022).
- Anaemia fact sheet, WHO, World Health Organization, 2025.
- Vitamin D, HSE, Health Service Executive (Ireland), accessed August 2026.
- Vitamins and minerals, NHS, National Health Service (UK), reviewed August 2020.
This page is for information only and is not a substitute for a medical consultation. Guideline links are provided for transparency; treatment decisions are made with your doctor.
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