If you feel weird after taking methylene blue, the first question is whether it is an ordinary side effect or a warning sign. Mild nausea, a headache, a bitter taste or blue urine are expected for some people. Agitation, confusion, a racing heart, heavy sweating, muscle twitching or a fever are not, especially if you take an antidepressant or another medicine, and they need urgent medical care. This guide covers the warning signs first, then the common reasons for feeling off and what to change, with what the research does and does not show.
The short answer
- Stop and get help for agitation, confusion, a racing heart, heavy sweating, twitching, rigid muscles or a fever. These can be signs of serotonin syndrome.
- Also urgent: a sudden severe headache with a pounding heart, yellowing of the skin or eyes, or swelling, hives or trouble breathing.
- Common and milder: nausea, headache, diarrhea, a bitter taste and blue or green urine all appear in methylene blue studies and prescribing information.
- The usual fixable causes: taking more than the label serving, taking it late in the day, taking it without food, or combining it with something that interacts.
- Don’t push through it. If a mild effect keeps coming back, stop and talk to your doctor.
Stop now: the signs that are not normal
Serotonin syndrome
Methylene blue is a potent, reversible inhibitor of monoamine oxidase A (MAO-A), the enzyme that breaks down serotonin. Combined with SSRIs, SNRIs, MAOIs or other serotonergic medicines, it can cause serotonin syndrome, which can be fatal. A 2010 systematic review found 26 patients who developed an acute confusional state after a methylene blue infusion, 24 of them taking a serotonin reuptake inhibitor. The prescribing information for the injectable hospital product lists the signs:
- mental changes such as agitation, hallucinations and delirium
- a fast heart rate, unstable blood pressure, dizziness, heavy sweating, flushing and a high temperature
- tremor, rigidity, muscle jerks, overactive reflexes and poor coordination
- seizures, and gut symptoms such as nausea, vomiting and diarrhea
Most cases appear within 6 to 24 hours of a new drug or dose change. If you notice these signs, stop methylene blue and get urgent medical care. Our guide to methylene blue and serotonin syndrome covers which medicines count and how long to wait between them.
A pounding headache with stimulants
The label for Adderall (amphetamine) lists intravenous methylene blue among the MAOIs it must not be taken with, or within 14 days of, because the combination raises the risk of a hypertensive crisis. A sudden severe headache, a pounding heart or chest pain after combining methylene blue with a stimulant is an emergency. Read our article on methylene blue and Adderall before combining them, and ask your prescriber.
Red blood cell breakdown
People with G6PD deficiency must not take methylene blue. The injectable’s prescribing information warns that it can cause severe breakdown of red blood cells and severe anemia in this group, and that anemia can appear a day or more after a dose. Yellowing of the skin or eyes, unusual weakness or breathlessness after taking methylene blue needs prompt medical attention, even if you have never been tested for G6PD deficiency.
Allergic reaction
Severe allergic reactions have been reported with methylene blue products. Swelling of the face or throat, hives or wheezing need emergency care.
Common reasons you might feel off
If none of the warning signs apply, these are the usual explanations. Side effects at 5 to 10 mg supplement servings have not been studied in detail, so what follows draws on studies of larger doses and on the product labels.
You took more than the label serving
The simplest cause is taking more than intended. The NooBlue labels are one 5 mg capsule daily with food, one 10 mg gummy daily, or drops measured at 0.5 mg per drop, so a 5 mg serving is 10 drops and a full dropper is 10 mg. Confusing a dropperful with a drop, or adding a second serving, multiplies the amount. Do not exceed the suggested serving. Our guide to how many mg of methylene blue per day explains label servings.
Nausea, taste and your stomach
Methylene blue tastes bitter and metallic. In a 2009 study where volunteers drank a 500 mg dose as a liquid, the taste caused nausea after 14 of 23 oral doses. The study also recorded a few cases of mild diarrhea and headache. The injectable’s prescribing information also lists headache, diarrhea and nausea among the reactions seen in 2% or more of 31 patients. Supplement servings are far smaller, but the same kind of reaction can happen. Take capsules with food, as our label says, and mix drops into water or juice.
You took it late in the day
Methylene blue has a half-life of roughly 14 to 24 hours, so a dose taken in the afternoon is still well above half its peak level at bedtime. If you feel wired, restless or sleep badly, take it in the morning. See our articles on the best time to take methylene blue, methylene blue and sleep quality and the methylene blue half-life.
Something else you took is interacting
Beyond antidepressants and stimulants, the injectable’s prescribing information names opioids and the cough medicine dextromethorphan as raising the risk of serotonin syndrome. Supplements that raise serotonin, such as St. John’s wort, count too. Check everything you take against our list of what not to take with methylene blue, and ask a pharmacist if you are unsure.
The blue urine surprised you
Blue or green urine is expected with every format and is not a sign that something has gone wrong. In the 2009 study it lasted several days after the large 500 mg dose. Here is why methylene blue changes urine color and what the color does and does not mean.
Dizziness or blurred vision
The injectable’s prescribing information tells patients not to drive or operate machinery until dizziness, confusion or eye symptoms have cleared, and lists blurred vision and palpitations among reported reactions. Those warnings come from hospital doses, but the advice applies at any dose: if you feel dizzy or your vision changes, do not drive, and stop taking it until you have spoken to a doctor.
Your appetite or energy changed
Some people report a change in appetite or energy. There is little research on this at supplement servings. We look at the appetite question in does methylene blue suppress appetite, and our overview of methylene blue side effects covers the wider list.
What to change, and when to stop
- Check your medicine and supplement list first. If anything on it is serotonergic or a stimulant, stop methylene blue and talk to your prescriber.
- Take no more than the label serving, at the same time each morning.
- Take capsules with food, and mix drops into water or juice.
- Give a fixed serving about a week before judging it, because levels build for several days. Our guide to how long methylene blue takes to work covers timing.
- If an effect keeps returning or gets worse, stop and talk to your doctor. Do not increase the amount to push through it.
Who should not take methylene blue
- People taking an SSRI, SNRI, MAOI or any other serotonergic medicine, because of the risk of serotonin syndrome.
- Anyone with G6PD deficiency.
- People who are pregnant or breastfeeding.
- Children and teenagers under 18.
Methylene blue can color urine blue or green. Talk to your doctor before use if you take any prescription medicine or have a kidney or liver condition. Our guide to who should not take methylene blue explains each group.
NooBlue makes methylene blue as 5 mg capsules, 10 mg gummies and 1% drops. You can read more about NooBlue or compare the formats in the NooBlue shop.
Frequently asked questions
Why do I feel weird after taking methylene blue?
Usually because of the amount, the timing or the taste: nausea, headache and a wired feeling are the common complaints. But agitation, confusion, a racing heart, sweating, twitching or a fever can be serotonin syndrome, especially with antidepressants, and need urgent medical care.
How do you know if you’re taking too much methylene blue?
Compare what you took with the label serving: one 5 mg capsule, one 10 mg gummy, or drops at 0.5 mg per drop. Nausea, headache, dizziness or poor sleep after a larger amount suggest you took too much. Do not exceed the suggested serving, and get medical help for any of the warning signs above.
What happens when you take methylene blue every day?
With a half-life of about a day, daily servings build up to a steady level over roughly three to five days, and urine stays blue or green. Long-term effects of daily supplement servings have not been studied in the papers we reviewed, so follow the label and review your use with your doctor.
Is the weird feeling methylene blue killing parasites?
There is no evidence for that. The feelings people call a die-off reaction match ordinary side effects such as nausea and headache. Treat any strong or worsening symptom as a reason to stop, not as a sign it is working.
How long does the weird feeling from methylene blue last?
Nobody has measured this at supplement servings. Oral methylene blue peaks in the blood about 2 hours after a dose and clears over several days, so a mild effect may come and go with each serving. If it lasts or returns, stop and talk to your doctor.
Should I stop taking methylene blue if I feel weird?
Yes, if the feeling is strong, new, or includes any warning sign above. For a mild effect, check the serving, timing and your other medicines, and speak to your doctor before continuing.
Sources
- ProvayBlue (methylene blue) injection, prescribing information. DailyMed
- Adderall (amphetamine mixed salts) prescribing information. DailyMed
- Ng BK, Cameron AJ. The role of methylene blue in serotonin syndrome: a systematic review. Psychosomatics. 2010;51(3):194-200. PubMed 20484716
- Ramsay RR, Dunford C, Gillman PK. Methylene blue and serotonin toxicity: inhibition of monoamine oxidase A (MAO A) confirms a theoretical prediction. British Journal of Pharmacology. 2007;152(6):946-951. PubMed 17721552
- Walter-Sack I, Rengelshausen J, Oberwittler H, et al. High absolute bioavailability of methylene blue given as an aqueous oral formulation. European Journal of Clinical Pharmacology. 2009;65(2):179-189. PubMed 18810398
- Simon LV, Torrico TJ, Keenaghan M. Serotonin Syndrome. StatPearls. NCBI Bookshelf
- St. John’s wort. National Center for Complementary and Integrative Health. nccih.nih.gov
