Itching all over the body without a rash: which blood values can help
The essentials at a glance
Itching without skin changes means: it itches, but nothing is visible on the skin apart from the marks caused by scratching. It can come from within. Four areas are documented: liver and bile, kidneys, iron stores, and thyroid (in essence according to Lonsdale-Eccles & Carmichael 2003). These include blood values that a medical practice can measure: GPT and gamma-GT for the liver, a kidney value, ferritin for iron stores, and TSH for the thyroid.
A single value does not decide anything. “A disease usually cannot be inferred from a single laboratory value.” The Institute for Quality and Efficiency in Health Care (IQWiG) states this on several of its laboratory value pages on gesundheitsinformation.de, 2025. A value is a starting point for a discussion in the doctor’s office, not a verdict.
This article categorizes the four directions, explains each of the values in half a sentence, shows the reference ranges in a table, and tells you when to stop reading and call. At the end, it explains what a blood test shows about this topic - and what it does not show.
What to expect in this article
1. Itching all over the body without a rash: why the skin does not have to be the source
2. What can be behind itching without skin changes
3. The four directions and their blood values
4. How common the four directions are
5. When you should stop reading and call
6. Three misconceptions about itching without a rash
7. What a blood test shows and what it does not
8. What you can do now
Frequently asked questions
Sources
Itching all over the body without a rash: why the skin does not have to be the source
It starts in the evening, when you come to rest. Back, forearms, calves, shoulders. You scratch, and in the morning you see scratch marks - but no hives and no redness that was there beforehand. Creams, changing detergents, shorter showers: tried, without effect.
The reflex to suspect the skin at this point is understandable. It is what you can see. But with itching without skin changes, it is not automatically where the explanation lies. Here, the itching is more like a warning light that comes on even though the light itself is not broken.
And what about the scratch marks? They are a consequence, not the cause. Scratching and scratch marks can alter the original condition of the skin - this is how the brief version of the S2k guideline on chronic itching describes it (in essence, based on Ständer et al. 2022). So if you scratched first and then see red streaks, that does not mean you have a rash. If, on the other hand, you see wheals or redness that was already there before scratching, you are better served by an allergic skin reaction than by this text. And if the itching is exclusively on your head, the relevant information is in itchy scalp.
Key takeaway
Itching is a cross-disciplinary key symptom of numerous diseases; the liver and bile ducts, kidneys, iron stores, and thyroid are four documented possibilities that may be behind it - and no single blood value can determine on its own which of them is involved.
You may already know this pattern from another context: one set of symptoms, several possible directions, one lab value for each, and ultimately the limit of what numbers can tell us. The same logic applies when assessing stiff joints in the morning. Itching is a different symptom, but the underlying logic is the same.
What may be behind itching without skin changes
Chronic itching is a cross-disciplinary key symptom of numerous diseases and is difficult to treat (in essence, based on Ständer et al. 2022). “Cross-disciplinary” means that it occurs in very different medical fields, not just in dermatology. For this reason, care should explicitly include cross-disciplinary diagnostics to identify the underlying disease causing it - looking for what lies beneath is therefore part of the treatment and not an unusual approach.
The guideline also states what this does to people. Chronic itching causes considerable distress: sleep disturbances, anxiety, low mood, and social withdrawal (in essence, based on Ständer et al. 2022). So if you say that the scratching bothers you most in the evening and at night, that is not a peripheral finding. It is the part of the problem addressed in the guideline. However, what the nighttime timing indicates about a cause is not stated there - the sources reviewed contain nothing on this, so there is nothing here either.
The second source is a review article from the journal Drugs & Aging that deals with itching in older people. Its key point, in essence: Before itching distributed across the entire body is considered age-related, an underlying condition should be sought. Thyroid diseases, iron deficiency, bile stasis, or impaired kidney function can be responsible for itching (paraphrased from Lonsdale-Eccles & Carmichael 2003). Bile stasis, medically known as cholestasis, means that bile does not flow out as it should.
The same paper makes a second point you should know: The mechanisms are poorly understood. So there is no clear chain of explanation from the thyroid to itching that someone could draw for you here. What does exist is the described association and the recommendation to investigate the underlying condition. This is exactly where blood values come into play.
Documented source
“AP is mainly measured when liver and bile duct diseases are suspected. This may be the case, for example, with symptoms such as widespread itching, jaundice, or dark-colored urine.”
Institute for Quality and Efficiency in Health Care (IQWiG)
gesundheitsinformation.de, “Alkaline phosphatase (AP),” 2025
The sentence shows that widespread itching can, in practice, be a reason to examine liver and bile values. For context: AP stands for alkaline phosphatase and is another liver value that a medical practice may measure. This article focuses on the two liver values GPT and gamma-GT. The article when liver values become critical explains in detail how far elevated liver values can go and when they start to play a role.
The four directions and their blood values
The table places the four directions side by side: which value belongs to each, what it measures, the range it should fall within in adults, and what it explicitly does not tell you. A reference range is the range in which the values of healthy people usually fall - it depends on the laboratory and method, and the information on your own test result is always authoritative.
Four directions, four values
| Direction | Which value | What the value measures | Reference range | What it does not tell you |
|---|---|---|---|---|
| Liver and bile | GPT (also ALT or ALAT) and gamma-GT (GGT) | GPT is an enzyme - a protein that initiates a reaction in the body - and is found mainly in the liver; elevated levels indicate liver damage. Gamma-GT is also an enzyme; elevated levels occur, among other cases, when bile flow is blocked (IQWiG 2025) | GPT in women aged 18 and over below 35 units per liter of blood (U/l), in men aged 18 and over below 50 U/l (IQWiG 2025). The verified sources do not specify a reference range for Gamma-GT. | “A single laboratory value usually cannot be used to conclude that a disease is present.” (IQWiG 2025) |
| Kidney | Cystatin C | A kidney value. The verified sources for this article contain no further information, so there is nothing more to state here | Dependent on the laboratory, with no value specified in the verified sources | “A single laboratory value usually cannot be used to conclude that a disease is present.” (IQWiG 2025) |
| Iron stores | Ferritin | Ferritin is a protein that can bind iron; the value indicates how much iron is stored in the body. A level below the reference range may indicate iron deficiency, while a level above it may indicate iron overload (IQWiG 2025) | Women over 18 years 9 to 140 micrograms per liter (µg/l), men over 18 years 18 to 360 µg/l (IQWiG 2025) | “A single laboratory value usually cannot be used to conclude that a disease is present.” (IQWiG 2025) |
| Thyroid | TSH | TSH, also called thyrotropin, is a hormone produced by the pituitary gland and released into the blood; elevated levels indicate an underactive thyroid (IQWiG 2025) | Adults 0.3 to 3.5 milli-units per liter (mU/l), from age 50 onward 0.3 to 4.5 mU/l; the ranges may vary from one laboratory to another (IQWiG 2025) | “A single laboratory value usually cannot be used to conclude that a disease is present.” (IQWiG 2025) |
Liver and bile: GPT and Gamma-GT
GPT is short for glutamate-pyruvate transaminase. The same value also appears on test results as ALAT or ALT. It is found mainly in the liver, and elevated levels indicate liver damage (IQWiG 2025). Gamma-GT, in turn, may be elevated in cases of liver inflammation, fatty liver disease, or a blockage of bile flow (IQWiG 2025). The last point is the link to the topic: A bile duct blockage is one of the four directions mentioned in connection with itching.
Kidney: Cystatin C
Impaired kidney function is one of the four directions (in the sense of Lonsdale-Eccles & Carmichael 2003). The kidney value referred to here is called Cystatin C. There is no verified institutional source for it available for this article, so it remains classified as “a kidney value” - without a reference range and without an explanation of how it is determined. What kidney values generally indicate is explained in the article Understanding kidney values in blood tests.
Iron stores: Ferritin
Iron deficiency is among the areas investigated when itching occurs (in the sense of Lonsdale-Eccles & Carmichael 2003); the documented signs of iron deficiency itself are pale skin, brittle nails, hair loss, fatigue, unusual exhaustion after exertion, and cracked skin at the corners of the mouth (IQWiG 2023). Itching is not included in this list of symptoms. The route to the iron stores leads through ferritin: In cases of iron deficiency, how well the iron stores are filled is determined using the ferritin level and the transferrin level (IQWiG 2023). The article Ferritin and iron: the difference explains how ferritin differs from iron in the blood.
Thyroid: TSH
The same distinction applies here: Thyroid disorders are among the areas investigated when itching occurs (in the sense of Lonsdale-Eccles & Carmichael 2003); the documented signs of an underactive thyroid are dry, especially doughy-thickened skin on the face, dry hair and hair loss, sensitivity to cold and feeling cold, as well as weakness and fatigue (IQWiG 2024). Itching is not listed there. An elevated TSH level in the blood can be a sign of an underactive thyroid (IQWiG 2024) - what an excessively high value means in detail is explained in the article TSH level too high.
How common the four areas are
None of the sources reviewed states what proportion of people with itching have an underlying internal cause. This figure is therefore not included in this article. What is available are figures for two of the four areas and the reference ranges for two values. They help put things into context, not interpret them.
Four documented figures
approximately 5 out of 100
People in countries such as Germany have an underactive thyroid (IQWiG 2024)
approximately 5 to 10%
of people in Europe are affected by iron deficiency (IQWiG 2023)
below 35 U/l
TSH reference range for women aged 18 and over (IQWiG 2025)
9 to 140 µg/l
Ferritin reference range for women over 18 years of age (IQWiG 2025)
Source: Institute for Quality and Efficiency in Health Care (IQWiG), gesundheitsinformation.de, 2023 to 2025
One of these figures is more relevant to you if you are a woman who has not yet gone through menopause: “Iron deficiency is more common in premenopausal women, mainly due to menstrual bleeding (menstruation)” (IQWiG 2023). This is not a statement about your itching. It is a statement about how likely it is that your iron stores are low in the first place - and therefore a reason not to overlook them when blood is being drawn anyway.
When you don't read, but call
There are two signs that should prompt you to close this article and call your practice: yellowing of the skin or eyes, also known as jaundice, and dark-colored urine. Both are mentioned in connection with widespread itching as reasons to determine liver and bile duct values (IQWiG 2025). What they mean in an individual case cannot be decided by anyone looking at a screen.
Without evidence, but based on simple common sense: If the itching lasts for weeks and keeps you awake at night, it belongs in the practice. Sleep disturbances are described in the guideline as part of the suffering (paraphrased from Ständer et al. 2022), and the guideline recommends investigating the underlying disease triggering it across medical specialties. It does not specify a time limit in weeks, and that is why this article does not specify one either.
The practice is not the authority here that forbids you from doing something. It is the authority that has access to examinations you cannot arrange yourself - and that combines your values with what it sees and hears from you.
Chapter at a glance
If your skin or eyes turn yellow, or your urine becomes dark, call your practice today. If the itching lasts for weeks or disrupts your sleep, make an appointment in the next few days. If it is new and your skin shows nothing, monitor it and keep notes. The sources reviewed do not specify a set time limit in weeks.
Three misconceptions about itching without a rash
Three statements stand in the way. All three lead in the wrong direction, and two of them can be refuted using the same sources cited above.
Myth check
Common
“If nothing is visible, you are imagining the itching.”
Proven
Chronic itching is a cross-specialty key symptom of numerous diseases and is associated with considerable suffering (paraphrased from Ständer et al. 2022).
Common
“Dry skin in winter is caused by the heating.”
Proven
Dry, especially doughy-thickened skin on the face, is one of the signs of an underactive thyroid (IQWiG 2024). This does not disprove the heating; it is simply not the only possibility.
Common
“A normal liver value rules out the liver.”
Proven
“A single laboratory value usually cannot be used to conclude that someone has a disease.” (IQWiG 2025) This applies in both directions: to an abnormal value and to an unremarkable one.
What a blood test shows and what it does not
The second reflex after scratching is the desire to find out for yourself. That is understandable, and an at-home test can be a starting point or a supplement to what is already being done in the practice. It is simply not a substitute for it. The test classifies values; it does not explain itching.
The test classifies values; it does not explain itching.
mybody®x (MYBODY Lab GmbH) offers a blood test for this purpose that includes the five values from this article. It is not designed for itching; it measures general values - four of them happen to relate to the directions discussed here. That is exactly how you should read it.
At-home blood test
Women's Wellness Check | Women's Health Test
18 values from capillary blood, including ferritin, TSH, GPT, gamma-GT, and the kidney value cystatin C - so at least one value for each of the four directions. The test does not provide a diagnosis and does not explain itching: "A single laboratory value usually cannot be used to draw conclusions about a disease." (IQWiG 2025)
A few drops from the fingertip, collected yourself
What the test cannot do is quickly listed. It does not tell you why it itches. It does not distinguish which of the four directions applies in an individual case. It does not replace the physical examination, and it does not replace the conversation in which someone asks how long this has been going on and what has changed in your everyday life. What it provides are numbers that you can bring with you.
What you can do now
Start with what costs nothing and makes the biggest difference in the conversation: Take notes. Since when has it been itching? Where on your body? At what time of day? Does it prevent you from falling asleep or wake you up? Did you start a new medication in the weeks beforehand - as a question for the practice, not as your own conclusion.
Take these notes with you to the appointment. A practice that receives your notes on a sheet of paper works differently from one that hears "it just itches." And if results are already available - from a test or an earlier blood draw - bring them along instead of interpreting them yourself.
The two signs from chapter five remain unaffected: yellowing of the skin or eyes and dark-colored urine are reasons to call today and not continue monitoring.
At the beginning was the question of why it itches even though nothing can be seen. The honest answer is that looking at the skin may be the wrong direction - and that these blood values mark the point where the search begins, not where it ends.
Frequently asked questions
Can itching without a rash come from the liver?
A bile duct obstruction, meaning impaired drainage of bile, is mentioned as a possible cause of itching (paraphrased from Lonsdale-Eccles & Carmichael 2003). IQWiG also states that liver and bile duct values can be tested for symptoms such as widespread itching, jaundice, or dark urine (IQWiG 2025). The two values discussed in this article are GPT and Gamma-GT. Whether they explain anything in your case is for the doctor’s office to determine, not the number.
Is a blood test enough to determine the cause of the itching?
No. The test categorizes the values; it does not explain the itching. It shows whether ferritin, TSH, GPT, and Gamma-GT are within their reference ranges - and even then, the following applies: “A single laboratory value usually cannot be used to infer a disease.” (IQWiG 2025) Investigating the underlying condition causing it belongs in a medical practice, across specialties (paraphrased from Ständer et al. 2022). A test can be a starting point or an addition, nothing more.
Why do I notice the itching more in the evening and at night?
The sources reviewed for this article do not say anything about this, so no interpretation is given here. What is documented is something else: Chronic itching causes considerable distress, including sleep disturbances (paraphrased from Ständer et al. 2022). So the fact that scratching in bed affects you most is described as a burden - just not as an indication of a specific cause. Mention the timing at your appointment rather than interpreting it yourself.
What does a ferritin level within the reference range mean?
Ferritin is a protein that can bind iron, and the level indicates how much iron is stored in the body (IQWiG 2025). For women over 18, IQWiG gives a range of 9 to 140 micrograms per liter; for men over 18, 18 to 360 micrograms per liter (IQWiG 2025). If the level is below this range, it may indicate iron deficiency; if it is above it, there may be too much iron in the body. A value within the range does not rule anything out on its own - reference ranges depend on the laboratory and method; your test result is what matters.
When should I go to the doctor about the itching?
Seek medical attention immediately if your skin or eyes turn yellow or your urine becomes dark - both are mentioned, along with widespread itching, as reasons to check liver and bile duct values (IQWiG 2025). Otherwise, make an appointment if the itching persists for weeks or disrupts your sleep. The sources reviewed do not specify a fixed number of weeks, so none is given here. The guideline recommends investigating the underlying condition causing it across specialties (paraphrased from Ständer et al. 2022).
Next step
Values to discuss at your appointment
If you want Ferritin, TSH, GPT, and Gamma-GT in black and white before making an appointment, you can find them in the Women's Wellness Check. It won't explain your itching - it gives you values to discuss.
Go to the Women's Health Test Liver values in detailRead more
You might also be interested in this
Why iron stores are particularly strained before menopause and which signs are documented.
What the values related to kidney function indicate and where their significance ends.
Sources
- Lonsdale-Eccles A., Carmichael A. J.: Treatment of pruritus associated with systemic disorders in the elderly, Drugs & Aging 20(3) (2003) - europepmc.org
- Ständer S. et al.: S2k guideline: Diagnosis and treatment of chronic pruritus, JDDG (2022) - europepmc.org
- IQWiG, gesundheitsinformation.de: Alkaline phosphatase (AP) (as of 2025) - gesundheitsinformation.de
- IQWiG, gesundheitsinformation.de: Alanine aminotransferase (ALAT) (as of 2025) - gesundheitsinformation.de
- IQWiG, gesundheitsinformation.de: Ferritin (as of 2025) - gesundheitsinformation.de
- IQWiG, gesundheitsinformation.de: Underactive thyroid (hypothyroidism) (as of 2024) - gesundheitsinformation.de
The four areas of liver and bile, kidneys, iron stores, and thyroid are based on [1]; key symptom, level of suffering, and scratch marks on [2]; the connection between widespread itching and liver and bile values on [3]; GPT and its reference range on [4]; ferritin and its reference range on [5]; signs and prevalence of underactive thyroid on [6]. Gamma-GT is taken from “Gamma-GT (GGT)” (IQWiG, 2025), the information on iron deficiency from “Iron deficiency and iron deficiency anemia” (IQWiG, 2023), and TSH and its reference range from “Thyroid-stimulating hormone (TSH)” (IQWiG, 2025). Product information, price, and parameter list are taken from the mybody®x product pages, accessed on 14.09.2026.
mybody®x Editorial & Specialist Team
Blood values Skin and symptoms Thyroid and iron
This article was created by the mybody®x specialist team and checked against the sources listed in the references. The people who contributed to and reviewed it are listed on the authors page.
Published on 14.09.2026 · Last updated on 14.09.2026
The content is for general information and does not replace medical advice, diagnosis, or treatment. Reference ranges depend on the laboratory, method, and age - the information on your test report is always authoritative.
Our products are not intended to diagnose, treat, cure, or prevent diseases.
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