Thyroid TSH Calculator
Hypothyroid symptom checker + TSH interpreter
Quick Answer
TSH (thyroid stimulating hormone) measures thyroid function. High TSH = underactive thyroid (hypothyroidism). 10% of women over 50 have hypothyroidism.
Normal TSH: 0.4 - 4.0 mIU/L | Above 4.0 = hypothyroid | Below 0.4 = hyperthyroid
Thyroid TSH FAQ
What is TSH and what does it measure?
TSH (thyroid stimulating hormone) tells your thyroid gland to make thyroid hormones (T3, T4). High TSH = underactive thyroid isn't making enough hormones. Low TSH = overactive thyroid making too much. Normal: 0.4-4.0 mIU/L. TSH is the most sensitive thyroid test.
What are symptoms of hypothyroidism (underactive thyroid)?
Top 8 hypothyroid symptoms: 1) Chronic fatigue, 2) Unexplained weight gain (10-20 lbs), 3) Always feeling cold, 4) Dry skin/hair loss, 5) Constipation, 6) Depression/mood swings, 7) Muscle weakness/aches, 8) Brain fog/poor memory. Women are 5-8x more likely than men. Affects 10% of women over 50.
Can thyroid problems cause weight gain?
YES! Hypothyroidism slows metabolism 5-40%, causing 10-30 lb weight gain (mostly water retention, not fat). Even mild hypothyroidism (TSH 4-10) causes weight gain. Treating hypothyroidism with medication (Levothyroxine) reverses weight gain in 3-6 months. Diet alone won't fix thyroid-caused weight gain.
What causes high TSH (hypothyroidism)?
Top causes: 1) Hashimoto's thyroiditis (autoimmune - 90% of cases), 2) Iodine deficiency (rare in developed countries), 3) Thyroid surgery/radiation, 4) Certain medications (lithium, amiodarone), 5) Pituitary gland issues. Risk factors: female, age 50+, family history, autoimmune diseases.
What foods help thyroid function?
Thyroid-supporting foods: Brazil nuts (selenium - 1-2 daily), seaweed (iodine), fatty fish (omega-3), eggs, chicken, oysters (zinc), dairy (iodine). AVOID with hypothyroid: raw cruciferous vegetables in excess (broccoli, kale - interfere with iodine absorption), soy (blocks thyroid hormone). Cook cruciferous veggies to deactivate goitrogens.
When should I start thyroid medication?
Medication (Levothyroxine) recommended when: TSH >10 mIU/L (always treat), TSH 4-10 + symptoms (often treat), TSH 4-10 + trying to conceive (treat). Goal TSH on medication: 1-2 mIU/L. Takes 6-8 weeks to see results. Medication is lifelong in most cases.
Can stress affect TSH levels?
YES! Chronic stress raises cortisol → suppresses thyroid function → increases TSH. Stress also worsens autoimmune Hashimoto's. Managing stress (meditation, yoga, 7-9h sleep) can lower TSH 0.5-1.0 mIU/L. Adrenal fatigue often coexists with hypothyroidism — treat both.
What's the difference between TSH, T3, and T4?
TSH = pituitary hormone that tells thyroid to work. T4 (thyroxine) = inactive thyroid hormone made by thyroid. T3 (triiodothyronine) = active form (converted from T4). Standard test: TSH only. If TSH abnormal, get Free T4 and Free T3. Some people have normal TSH but low T3 (conversion issue) — still have symptoms.
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See All →This is not medical advice — talk to your doctor. The sections below are educational only. This calculator does not diagnose hypothyroidism, hyperthyroidism, or any thyroid condition, and results should not replace lab testing or guidance from a healthcare provider. Do not start, stop, or change any thyroid medication based on this tool alone.
Thyroid Basics: TSH, T4, and T3 Roles
The thyroid is a small gland in the neck that makes hormones controlling metabolism, energy, temperature, and heart rate. Three lab values matter most:
| Marker | What It Is | Common Range |
|---|---|---|
| TSH | Pituitary signal to the thyroid | 0.4–4.0 mIU/L |
| Free T4 | Main thyroid hormone (inactive) | 0.8–1.8 ng/dL |
| Free T3 | Active form (converted from T4) | 2.3–4.2 pg/mL |
TSH is the first test. If it is abnormal, free T4 and free T3 are added. Ranges vary by lab — your doctor interprets the full panel in context.
TSH Bands Explained
This is how the calculator maps a TSH value to a band (educational cut-offs, not clinical thresholds):
| Band | TSH (mIU/L) | Meaning |
|---|---|---|
| Hyperthyroid | Below 0.4 | Possible overactive thyroid |
| Normal | 0.4–4.0 | Healthy thyroid function |
| Subclinical hypo | 4.0–10.0 | Mild underactive — may need follow-up |
| Overt hypo | Above 10.0 | Underactive — discuss with your doctor |
Some guidelines use a tighter upper limit (around 2.5 to 3.0 mIU/L) in pregnancy. A single abnormal result is usually confirmed with a repeat test before any treatment decision.
Hypothyroid vs Hyperthyroid Symptoms
Hypothyroid (underactive)
- Fatigue, low energy
- Unexplained weight gain
- Feeling cold
- Dry skin and hair
- Constipation
- Depression, low mood
- Muscle aches and weakness
- Brain fog, poor memory
Hyperthyroid (overactive)
- Unintended weight loss
- Rapid or irregular heartbeat
- Feeling hot, sweating
- Anxiety, irritability
- Tremor (shaky hands)
- Frequent stools
- Insomnia
- Enlarged neck (goiter)
These lists overlap with many other conditions. Symptoms alone do not diagnose thyroid disease — a TSH blood test does.
How the Assessment Works
The tool takes your TSH value, places it into a band, and counts your checked symptoms:
Formula (educational)
Band = TSH cut-off range (below 0.4, 0.4–4.0, 4.0–10.0, above 10.0)
Symptom score = count of checked symptoms (0–8)
A high symptom count with a normal TSH still warrants a doctor visit, because symptoms can precede lab changes or point to another condition. The band is a prompt to discuss with your doctor, not a diagnosis.
What Affects Thyroid Labs: Illness, Meds, Time of Day
| Factor | Effect on TSH |
|---|---|
| Time of day | TSH peaks overnight and early morning — test in the morning |
| Recent illness | Can temporarily lower TSH (non-thyroidal illness) |
| Steroids / dopamine | Can lower TSH acutely |
| Biotin supplements | Can falsely alter TSH and T4 — stop 2–3 days before testing |
| Pregnancy | Reference ranges shift — hCG affects TSH in early pregnancy |
| Thyroid medication timing | Take on an empty stomach; test before taking the dose |
This is why a single abnormal result is usually confirmed with a repeat test under stable conditions before any treatment decision.
Worked Example
A 45-year-old woman enters TSH = 6.5 mIU/L and checks 5 symptoms (fatigue, weight gain, cold intolerance, dry hair, brain fog).
Calculation
TSH = 6.5 → Subclinical hypo band (4.0–10.0)
Symptom score = 5/8 (above the 4-symptom prompt)
Band: Subclinical hypothyroid with multiple symptoms
This result would prompt a doctor visit to confirm with a repeat TSH, add free T4 and anti-TPO antibodies, and discuss whether treatment or monitoring is appropriate. The score is a prompt to seek testing, not a diagnosis.
How to Use This Calculator & What to Do With Your Result
How to use it:
- Enter your TSH level in mIU/L from a recent blood test.
- Check any hypothyroid symptoms you have been experiencing.
- Click "Analyze Thyroid Function" to see your band and symptom score.
What to do with your result:
- If your band is normal and symptoms are few, retest every 1 to 2 years or if symptoms develop.
- If subclinical (4 to 10), ask your doctor about a repeat test in 6 to 8 weeks and a full panel.
- If overt (above 10), or if you have 4+ persistent symptoms, bring your result to your doctor promptly.
- Use the Hormone Balance Calculator and Metabolic Age Calculator to explore related symptoms.
- Do not start, stop, or change any thyroid medication based on this result alone — talk to your doctor first.
Limitations of This Calculator
- It places a self-entered TSH value into educational bands — it does not measure TSH or diagnose any condition.
- Reference ranges vary by lab and by guideline — the cut-offs are general, not universal.
- Symptoms are self-reported and overlap with many other conditions (anemia, depression, sleep apnea).
- It does not account for pregnancy, recent illness, biotin supplements, or medication timing.
- It does not include free T4, free T3, or antibodies — a full panel is needed for diagnosis.
- It cannot diagnose hypothyroidism, hyperthyroidism, Hashimoto, or any thyroid condition — that requires lab testing and a doctor to interpret.
When to See an Endocrinologist: Doctor Guidance
Talk to your doctor about a thyroid blood test if any of these apply:
- You have 4 or more persistent thyroid symptoms lasting several weeks.
- Your calculator result falls in the subclinical or overt band.
- You have a family history of thyroid or autoimmune disease.
- You are pregnant or planning pregnancy (TSH targets are tighter).
- You have type 1 diabetes or another autoimmune condition.
Your primary doctor can order TSH and free T4. An endocrinologist is usually involved for complex cases, pregnancy, nodules, or unstable results.
Disclaimer: This thyroid TSH calculator provides an educational band for a self-entered TSH value and a symptom check. It does not diagnose hypothyroidism, hyperthyroidism, Hashimoto, or any thyroid condition, and does not recommend or adjust any thyroid medication (including levothyroxine). Only a healthcare provider can order and interpret lab tests and set a treatment plan. This is not medical advice — talk to your doctor.